Consider that it’s canon that Saitama and Genos live together in a small one room apartment. That they go shopping together, eat together, go to the bath house together, brush their teeth together.
Consider that Genos cooks, cleans, does the dishes and laundry not because he’s asked to, but because he wants to help Saitama. That he buys all his merch, wears a shirt with his face on it and has a photo of Saitama as his phone’s background. That he makes food with Saitama’s face on it, which they bring to a HA picnic as a smiling Genos pours them drinks.
Consider that Fubuki recognizes Genos not because he’s the one blond cyborg hero, but because he starts going on about his “sensei”. That he tells Don Pacino that he’d do anything for Saitama. That he tells Saitama, to his face, that he is the most amazing person he’s ever met, that he will always follow him no matter what others think of him. That when Saitama tells him how he feels lonely, Genos cries and asks him to wait until he can stand by his side.
Consider the lyrics of the ED, which includes lines like “when I close my eyes, you’re all I think about, “feeling the need to see you, feeling like crying, feeling romantic” and “the one I love is so strong they make me worry”. That a magazine pointed out that it takes a lot to not imagine that these are Genos’ thoughts. That the singer and Genos’ VA have expressed similar opinions.
Consider that the VAs on both sides of the pond joke about how much of a couple they are. That there’s a clip of them making hand puppet versions of them kiss. That they filled the OPM festival with double meanings, like making it sound like Genos was asking Saitama to go out with him. That magazines have described Genos as ignoring his fangirls because he’s “only attracted to Saitama’s power” or that he’s “infatuated” with him”. That the English VAs have tweeted that “Genos loves his master”, that maybe next time they will go on an actual date. That Saitama’s VA signed a fan’s print with “I ship it too”.