Kanoko and Yamada have a good relationship. Yamada knows how to read the mood during their meetings and Kanoko notices this. During Kanoko's birthday Yamada noticed Kanoko had become cuter since their middle school days and joked about asking her to date him. They talk normally but aren't particularly close.
Yamada and Natsukusa go to the same high school and seem to be really close. Yamada will do anything in his power to help Natsukusa get closer to Momoka. Natsukusa was one of the few people to congratulate Yamada during his birthday.
Yamada thinks Momoka is really cute and tries his best to help Natsukusa get closer to her. They don't talk much but Yamada is observant enough to know she was ostracized in middle school and to realize Momoka's feelings towards Kanoko.