A little concerning that there so much death teenage lesbians, unless they just have been ghost for a long time, but still weird. Better to not think about it too much.
Interestingly, lovers' suicide was quite common during Japanese high-school girls at one point in Japan's history, since many of them fell in love with their classmates in all-girls' schools and couldn't deal with being whisked away at graduation to be pushed into obligatory het marriages. All those melodramatic, depressing Class S manga from the 80s and 90s were based, to an extent, in reality. I recommend watching Zeria's video series on the history of the yuri genre for more info.