The Protagonist of Housamo is made up 24 souls of Transients that were exiled from their world for one reason or the other. Some of these exiles also appear in FGO (Tiamat, Quetzalcoatl, Ushiwakamaru, and Kamadeva) and while it's not confirmed, the exile from The World of the Old Ones might be Cthulhu. Also the Seth seen here is the real one (the "Seth" in the game is Ash) and he along with the rest of the exiles are giving their powers to the Protagonist so they can fight and protect their friends and loved ones in their stead. I was tempted to add Sitonai because she's part Freyr like MC5 but there's already enough girls in here. Besides, I want to show off MC5 some more.

MC5 muzina_kodanuki
Seth by siba81715928
Quetzalcoatl by 野生の何か
Tiamat and Kama by AkaneChi00
Ushiwakamaru kingM01535665
Cthulhu Oyabun
© Lifewonders Tokyo Afterschool Summoners
© Type Moon Fate/Grand Order