[Reincarnated]

Spoiler:

From my point of view, Riku hasn't rejected Rena.... yet. They're interupted by the noise of some fightings between Jinki users and then Rena realized something (IMO she assumed she gave Riku more burden, because at the first page of the chapter Rena screamed for help in her mind...) thus she ended up lying to Riku that she likes him as a "partner" or "family".

After that she ran away and left behind a letter that explains things, including her confessing once more to Riku that she actually love him not as a partner, not as a family,and not as a friend. It really does seem like her last words.... I really hope not. Please don't.