KakeruxNaho. Because that's who she loved. And don't get me wrong, I loved Suwa to pieces, but if Kakeru hadn't committed suicide, there's no doubt in my mind that he would not have even stood a chance. She loved Kakeru up to the very end and for a long time afterwards--I believe she still did even once she's married Suwa.
And for the record, Naho didn't think that she could heal Kakeru by being his girlfriend
. She just tried to show him that she loved him and wanted him around, as did his other friends. She just happened to fall in love with him in the process.And let's not forget that these were kids. I can't speak for the adult Naho, but the young Naho was not really equipped to properly deal with depression and suicidal thoughts. Hell, most adults in the real world can't even properly deal with it when friends and/or family member suffer from it, so I think we can cut the kid some slack.