this is just my speculation and im basing this off google translate, but I think that item is specifically for leveling himes quickly
maybe when u use those, they gain like a huge amount of levels in an instant? or maybe max leveled immediately or something since that is a gacha promo
Shinki usually refers to himesOriginally Posted by Google translated line from 【DMM】神姫PROJECT/_A Twitter
and I saw the words enhance and level up so that's why I thought its probably like that
and if im right, they probably made this for the whales that are too lazy to level all their himes lol (since they have a lot)
(feel free to correct me if im wrong though)