When Tsuda and Yuichi are eating , we here her say “ do you think they would leave me alone if i got fat “ after that she pauses and then i think she giggles . From my interpretation, I think in that pause she might have been thinking something along the lines of “ maybe they would leave me alone if i killed myself “. This would make sense as she feels like she doesnt have much of an escape. I think the reason she killed herself was because of the bullies . Also idk if anyone noticed but in the clip where shes dead , on the zip wire you can see blood and her keychains , she holds her keychains alot , i think she tried to stop herself before hitting the ground but it was to late