<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019fdd44-e3e5-769c-94b9-44c7d09ef78e,g:ff06b72d-961e-4ce5-a495-cee9004d261b-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:roleRef roleURI="http://www.mainstcapital.com/role/Cover" xlink:type="simple" xlink:href="msif-20261008.xsd#Cover"/>
  <link:presentationLink xlink:role="http://www.mainstcapital.com/role/Cover" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_CoverAbstract_019fdd44-e3e5-7ee7-8e67-6fe1a9189e69" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_CoverAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_019fdd44-e3e5-7d12-bd37-0ddb2d56d287" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentType"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019fdd44-e3e5-7ee7-8e67-6fe1a9189e69" xlink:to="loc_dei_DocumentType_019fdd44-e3e5-7d12-bd37-0ddb2d56d287" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_019fdd44-e3e5-771e-b516-a43a1e2954f9" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentPeriodEndDate"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019fdd44-e3e5-7ee7-8e67-6fe1a9189e69" xlink:to="loc_dei_DocumentPeriodEndDate_019fdd44-e3e5-771e-b516-a43a1e2954f9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_019fdd44-e3e5-7baa-b402-ec0742ff028a" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityRegistrantName"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019fdd44-e3e5-7ee7-8e67-6fe1a9189e69" xlink:to="loc_dei_EntityRegistrantName_019fdd44-e3e5-7baa-b402-ec0742ff028a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_019fdd44-e3e5-7ad6-aa79-c542467a4445" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019fdd44-e3e5-7ee7-8e67-6fe1a9189e69" xlink:to="loc_dei_EntityIncorporationStateCountryCode_019fdd44-e3e5-7ad6-aa79-c542467a4445" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_019fdd44-e3e5-73e3-b1a6-b10c25760cac" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityFileNumber"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019fdd44-e3e5-7ee7-8e67-6fe1a9189e69" xlink:to="loc_dei_EntityFileNumber_019fdd44-e3e5-73e3-b1a6-b10c25760cac" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_019fdd44-e3e5-7f38-a451-31e7633c4913" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019fdd44-e3e5-7ee7-8e67-6fe1a9189e69" xlink:to="loc_dei_EntityTaxIdentificationNumber_019fdd44-e3e5-7f38-a451-31e7633c4913" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_019fdd44-e3e5-7e3a-9ba4-e33d75124097" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressAddressLine1"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019fdd44-e3e5-7ee7-8e67-6fe1a9189e69" xlink:to="loc_dei_EntityAddressAddressLine1_019fdd44-e3e5-7e3a-9ba4-e33d75124097" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine2_019fdd44-e3e5-7669-85c1-53fd91b3ae27" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressAddressLine2"/>
    <link:presentationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019fdd44-e3e5-7ee7-8e67-6fe1a9189e69" xlink:to="loc_dei_EntityAddressAddressLine2_019fdd44-e3e5-7669-85c1-53fd91b3ae27" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_019fdd44-e3e5-76fb-ac73-9ec7a96fff3b" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressCityOrTown"/>
    <link:presentationArc order="9" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019fdd44-e3e5-7ee7-8e67-6fe1a9189e69" xlink:to="loc_dei_EntityAddressCityOrTown_019fdd44-e3e5-76fb-ac73-9ec7a96fff3b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_019fdd44-e3e5-7b27-ba8b-1a6ee937b065" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressStateOrProvince"/>
    <link:presentationArc order="10" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019fdd44-e3e5-7ee7-8e67-6fe1a9189e69" xlink:to="loc_dei_EntityAddressStateOrProvince_019fdd44-e3e5-7b27-ba8b-1a6ee937b065" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_019fdd44-e3e5-7b21-a526-4711448dd60d" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressPostalZipCode"/>
    <link:presentationArc order="11" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019fdd44-e3e5-7ee7-8e67-6fe1a9189e69" xlink:to="loc_dei_EntityAddressPostalZipCode_019fdd44-e3e5-7b21-a526-4711448dd60d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_019fdd44-e3e5-7065-a2c9-f4a2999bbe57" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_CityAreaCode"/>
    <link:presentationArc order="12" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019fdd44-e3e5-7ee7-8e67-6fe1a9189e69" xlink:to="loc_dei_CityAreaCode_019fdd44-e3e5-7065-a2c9-f4a2999bbe57" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_019fdd44-e3e5-7bd1-8d9a-5cbb7ffd924a" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LocalPhoneNumber"/>
    <link:presentationArc order="13" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019fdd44-e3e5-7ee7-8e67-6fe1a9189e69" xlink:to="loc_dei_LocalPhoneNumber_019fdd44-e3e5-7bd1-8d9a-5cbb7ffd924a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_WrittenCommunications_019fdd44-e3e5-7b5a-8ba9-d6a69e330beb" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_WrittenCommunications"/>
    <link:presentationArc order="14" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019fdd44-e3e5-7ee7-8e67-6fe1a9189e69" xlink:to="loc_dei_WrittenCommunications_019fdd44-e3e5-7b5a-8ba9-d6a69e330beb" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SolicitingMaterial_019fdd44-e3e5-760b-b646-7504229808f1" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_SolicitingMaterial"/>
    <link:presentationArc order="15" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019fdd44-e3e5-7ee7-8e67-6fe1a9189e69" xlink:to="loc_dei_SolicitingMaterial_019fdd44-e3e5-760b-b646-7504229808f1" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementTenderOffer_019fdd44-e3e5-721a-9279-cd97daa7bfe0" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_PreCommencementTenderOffer"/>
    <link:presentationArc order="16" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019fdd44-e3e5-7ee7-8e67-6fe1a9189e69" xlink:to="loc_dei_PreCommencementTenderOffer_019fdd44-e3e5-721a-9279-cd97daa7bfe0" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementIssuerTenderOffer_019fdd44-e3e5-7d3f-b6a7-b647a6967d12" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_PreCommencementIssuerTenderOffer"/>
    <link:presentationArc order="17" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019fdd44-e3e5-7ee7-8e67-6fe1a9189e69" xlink:to="loc_dei_PreCommencementIssuerTenderOffer_019fdd44-e3e5-7d3f-b6a7-b647a6967d12" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_019fdd44-e3e5-7196-9575-077e54047e09" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:presentationArc order="18" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019fdd44-e3e5-7ee7-8e67-6fe1a9189e69" xlink:to="loc_dei_EntityEmergingGrowthCompany_019fdd44-e3e5-7196-9575-077e54047e09" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_019fdd44-e3e5-7134-9b7b-0555402230d2" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCentralIndexKey"/>
    <link:presentationArc order="19" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019fdd44-e3e5-7ee7-8e67-6fe1a9189e69" xlink:to="loc_dei_EntityCentralIndexKey_019fdd44-e3e5-7134-9b7b-0555402230d2" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_019fdd44-e3e5-7d86-9a4c-c08f3ddd1525" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_AmendmentFlag"/>
    <link:presentationArc order="20" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019fdd44-e3e5-7ee7-8e67-6fe1a9189e69" xlink:to="loc_dei_AmendmentFlag_019fdd44-e3e5-7d86-9a4c-c08f3ddd1525" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityListingsTable_019fdd44-e3e5-70e9-b5a4-e6ffb1f9fcb2" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityListingsTable"/>
    <link:presentationArc order="21" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019fdd44-e3e5-7ee7-8e67-6fe1a9189e69" xlink:to="loc_dei_EntityListingsTable_019fdd44-e3e5-70e9-b5a4-e6ffb1f9fcb2" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityListingsLineItems_019fdd44-e3e5-7ee8-bf2b-cc8431579e4f" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityListingsLineItems"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityListingsTable_019fdd44-e3e5-70e9-b5a4-e6ffb1f9fcb2" xlink:to="loc_dei_EntityListingsLineItems_019fdd44-e3e5-7ee8-bf2b-cc8431579e4f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_019fdd44-e3e5-794a-bb98-0cb7b3ef2854" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_Security12bTitle"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityListingsLineItems_019fdd44-e3e5-7ee8-bf2b-cc8431579e4f" xlink:to="loc_dei_Security12bTitle_019fdd44-e3e5-794a-bb98-0cb7b3ef2854" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_019fdd44-e3e5-7101-96a4-9eb148033d3b" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_TradingSymbol"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityListingsLineItems_019fdd44-e3e5-7ee8-bf2b-cc8431579e4f" xlink:to="loc_dei_TradingSymbol_019fdd44-e3e5-7101-96a4-9eb148033d3b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_019fdd44-e3e5-70eb-b1d0-5e1a980199df" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_SecurityExchangeName"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityListingsLineItems_019fdd44-e3e5-7ee8-bf2b-cc8431579e4f" xlink:to="loc_dei_SecurityExchangeName_019fdd44-e3e5-70eb-b1d0-5e1a980199df" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
</link:linkbase>
