Wow. The novel translation has Lily's "grownup" transformation at middle schooler, NOT late teens/early 20s. Her lack of sexual maturity seems to form a decent part of her character. "Ageing" up her true form will change the relationship dynamics quite a bit from the WN. (I guess she was aged up in the LN??? Though the V2 cover seems to have Lily more 13-14 than 18-22)