The world of Type-Moon starts with saving Altria!

As a master who traveled through time, Ian is not very familiar with Chaldea.
But it doesn't matter, he has a special ability that other masters don't have - that is the simulator.
This allowed him to leave his mark in history.
——Although it’s not quite normal.
[You became the husband of the demon concubine, but at the same time you cheated on the Holy Knight King who was disguised as a man. Britain is in a mess because of you. ]
[You controlled Tamamonomae, and as your master, you let Minamoto no Raikou witness what physical demon exorcism is. The demons of the Heian era all avoided you. ]
[You made Medusa lose her mind, and all of Greece echoed her words that she would take off her blindfold the moment she met you again.]
[You are Joan of Arc's soul mate. Only you know how to make this usually extremely reserved saint feel liberated and relaxed in every sense.]
Ian had to say that this simulator that understood people's hearts was perfect for him.
Solve all problems in his favorite way.
Everything looks good.
Until the moment they came to him.