saddest character? spoilers

Issei (ramen guy) - one sided love for nao and puts it on the line for her with nothing in return. Frequently is a third wheel and even his stalker rejects him after one day with him.

Daichi - obsessed with nao for years and defended her for nothing in return, barely mentioned by her after leaving

Uehara - unable to express his emotions and will likely end up an outcast once his popularity fades past high school, constantly dragged into unwanted drama. Seems to have very few real friends except Nao.

Nao - loves uehara but is treatedly coldly and is miserable half the time, can't stand up to bullies, can be somewhat delusional

Yuri - somewhat insane and constantly suspecting her partner of cheating, yet wont leave him

Which character is the saddest?