When I think about it more, the flower on Hikari's head symbolizes a brain illness. She kept her feelings to herself just so she wouldn't burden her sensei because it was worsening. She was bedridden and couldn't go to school. Sensei visited her and couldn't help but to confess anyway, and witnessed Hikari's last breath.

Those plants growing underneath those bandages Sensei was wearing were probably due to self-harm. She wanted to join Hikari so badly but waited until graduation. It was quite fishy because she knew when she would die after one of the students said she was retiring that year because Hikari didn't, which means she planned it all out. She ended her own life just to be with Hikari.

And now, they're together.

Homie, you had no business making me cry for like ten minutes.