This is my own personal theory.
Since laughter, smiling, and children are quite a common thing in 2kki, I always thought Urotsuki had been bullied and humiliated heavily. She used to have one friend, Aojiru, but eventually he was bullied too due to being friendly with Uro, and left her side to join in with the persecutors. I thought this because he ignores every effect, showing he now doesn't acknowledge her unless he's teasing or hurting her. Like in >>608
, Urotsuki lied to her parents about her injuries. Eventually, it got too much, and she managed to get hold of a chainsaw and killed them all, and hospitalized Aojiru, but wishes to murder him still, which is why her first reaction is to kill him. I think Broken Faces World references the bullies she killed, because they are all deformed in there. That world also includes Surimuki, as I mentioned before about the cuts. The UFO entrance is her wish to go somewhere else, like her home (Appartments) or a forest. (Fairy Tale Woods) After the people she had killed were gone, she had to start afresh, which references the killing of the 'Grey Urotsuki' somewhere I can't remember. It is her getting rid of her boring side and becoming colorful and fun, like Marijuana World. When she became popular herself, she succumbed to peer pressure and took drugs, evidenced in Marijuana Goddess World, Smoking HAL and Mushroom World. The Boy, Gakuran, Bike and Chainsaw effects are all quite 'boyish', which shows that could've been the reason she was bullied? I could probably fit a lot of effects into this theory, for example Tissue representing her wiping away her tears.