About Tatsuki Edit
One theory is that Tatsuki and Lefia are related. Lefia was the favored child, which is why she appears as a princess. Tatsuki was ignored by his parents and bullied at school, and, seeing no other option, Tatsuki closed himself to his room.
Before closing himself off, Tatsuki was friends with the chaser girl, who verbally abused him. However, Tatsuki did not care at this point due to being neglected by everyone, and wanted to stay with the girl because she was the only one who paid any attention to him. He started to believe all of her harsh words, and referred to himself as "idiot" to appease her. He often fantasized about standing up to her, or even killing her, but never had the strength to do it.
Tatsuki may have self-harm issues, being signified by the scissors he wields. His one sleeve is rolled up to show off the cuts, hoping that someone will see them and try to help him. There are many reoccurring sharp objects in Tatsuki's dreams, including many references to glass. Maybe he uses glass shards to cut himself as well.
Tatsuki's self-hatred is a re occurrence in his dreams as well, shown in the many events where he hurts another version of himself, or dies in some way.