Fate/stay night - Baka-Tsuki

Fun fact: there was a digital card game called Fate/Zero: Next Encounter that featured alternate Master/Servant pairings : r/grandorder

Mushi Uta - Baka-Tsuki

Baka-Tsuki

Fate/Zero (Novel) - Baka-Updates Manga

Fate/stay night, TYPE-MOON Wiki

Madan no Ou to Vanadis - Baka-Tsuki

A Magus' worst fear : r/grandorder

Shinmai Maou no Keiyakusha:Volume 8 - Baka-Tsuki

Fate/Zero:Volume4 Full Text - Baka-Tsuki

Fate/Zero - Baka-Tsuki

Mushoku Tensei - Baka-Tsuki

Maru-MA - Baka-Tsuki