I don't know why I spent the last two hours trying to think of a reason why a child Taiga Fujimura would show up as Faust's Master. After sitting there staring at a wall for some time I came to three conclusions.

1) Zelretch is trolling everyone with child Taiga.

2) It's actually the child of Taiga and Shirou.

3) This is a really bad idea.

Whelp, now to make a sweet old lady for Faust to get sweets from.