This falls into the same timeline with the whole Yae Miko shrinking Lumine/Aether or your own persona character. Also, the title isn't a lie. This drops right into place when Mavuika mentions a reward that can be asked for.

Mavuika is of age as I do not need to age her up. Ai art is made by me, so the image may show Lumine, but again you can be her, Aether or your own persona character.