...

no i think he blames himself for the death of his former lover (who committed suicide)

Oh.. now everything makes sense.. thank you.

I thought he fell of the cliff?! not suicide? o.O

We don't really know. He fell off the cliff for sure but whether or not it was suicide... the sister is convinced that her brother committed suicide, but again, she can be wrong. We just have to wait till it's clarified ;)

I'm pretty sure it was suicide. Because it's an ugly word with such heavy implications, it's difficult for family to accept much less say the keyword. she's just blaming the seme because she couldn't and didn't do anything to stop him, the whole "what ifs".