I love Yuu's so much. Each of them had a goal or a dream before arriving in TWST and if time there runs parallel to time in Twisted Wonderland, then all their hard work has gone to waste. Their family and friends must be worried about them. It's so tragic and scary.
Malleus and Yuu have both expressed feelings of uselessness or futility several times now, so maybe this will be part of their story in Book 8 as they help each other feel more confident in their self-worth, as well as a greater sense of belonging π₯Ί