Shou Hibayashi's Links
Mori, being Shou's older sister, is someone that Shou would do anything to protect. He also admires her work ethic, and hopes that when he gets older, he can get himself in the same field that Mori is in. The two of them also understand each other's social difficulties rather well -- with Shou often taking some of the social brunt whenever he can tell that Mori can't handle it for the day.
Shou is Mori's younger brother, and would do anything to make sure that he is loved and safe. She built Mothman.exe in hopes that he could help Shou have an easier time growing up, and sometimes wishes she had more time away from her work to be with him.
Mothman is an idiot, but he is Shou's idiot, and that's what matters. Shou sees Mothman as the parental figure that he doesn't really have, and heavily relies on him to speak to others due to his selective mutism.
Mothman was built first and foremost by Mori to look out for Shou, so naturally, Mothman likes Shou a lot! He looks out for Shou a great deal, and makes the efforts to cheerlead him whenever Shou tries to push himself out of his very, very tight comfort zone.
Prior to their disappearance, Shou didn't particularly care much for Yuu - as with most people, really - but began to worry about them when their reasoning for their disappearance was tied back to DRcade's infamy. He's been helping Mori try and find them now.
Yuu had some shared understanding with Shou due to the two's shared distaste in social situations. Neither really interacted much as a result, though - and thus, Yuu doesn't hold especially positive feelings towards him after DRcade's downfall.