oh yes iwa is probably a bit dense like no shade to his character but i don’t think he would understand what’s happening and kind of just go blank lmao i think tendou would def be flustered but he’s kind of good at hiding it by teasingly flirting with iwa and omg they’re both a mess lmao oikawa would most definitely take a bunch of videos and pictures of them and fake disgust but he’s actually so happy for iwa and ushi has to be told what’s going on bc he just thinks they’re good friends lmao
yeah exactly! i feel like he wouldn't be totally oblivious, at least not about tendou's flirty behavior. he's not sure if it's just mocking or real flirting but DOES realize he's being hit on, what he DOESN'T realize is the effect he and his actions have on tendou. for example this thing where he just rolls up his t-shirt's sleeves. he does that all the time, who could've known it makes tendou's brain stop working for a second?? so yeah he's kinda dense but only, or mainly, about his own part in that flirting
weeell as you said, they're both a mess. the only difference is that one of them is turned into it on purpose and the other one basically by accident.
i feel like oikawa's reaction is literally the best thing about this whole ship because it's a huge conflict for him at first. iwaizumi is his best friend and of course he wants him to be happy but come on tendou satori are you kidding me iwa-chan! and he pouts and makes fun of them but then he realizes that this is really fucking serious. gosh i have a scenario in my head, i'm sorry but hear me out: it's canon that oikawa sometimes jokes about iwaizumi being stupid or ugly. and it's not like iwaizumi never dated anyone before and he never asks oikawa to do so but he always comes around to look at the outfit iwaizumi picked. and he always says something like "oh wow what a great outfit to scare them away" and normally iwaizumi just gives him a smack on the back of his head or kicks him and then leaves the way he is because it's just kidding around and he knows that. so when he has a date with tendou oikawa comes around and his comment is: "luckily they don't have standards at shiratorizawa, iwa-chan". now he expects the usual kick but nothing happens. iwaizumi just checks himself in the mirror, again and again and again and realization dawns on oikawa; "shit this time it's different" and he just pulls iwaizumi into a hug and says "you look gorgeous, now go and get yourself a boyfriend" and that's it. he accepts the relationship. aaaaah i'm sorry this was supposed to be a nice short answer jdbdisp
anyways YES oikawa ships it, oikawa loves it but he doesn't show it. comments like "get a room" and "attention, love birds ahead" all. the. time.
but he's happy for his best friend and also takes great pleasure in confusing ushijima - "but are they REALLY together? as a couple? well i'd say yes, but who knows? i tell you who DOESN'T know and that's you! you WOULD know tho if you would've come to seijouh where we talk about such stuff!" (they don't. iwaizumi only told oikawa who accidentally blurted out that iwaizumi's in a relationship and makki and mattsun literally tickled it out of iwaizumi so they could tell the rest of the team)