Ichigo is so OOC around Orihime because he’s not an asshole to her. He’s rude to people he feels comfortable with, and if he can’t be like that to Orihime, it means that he’s not comfortable with her and so Ichihime is OOC
Firstly, I don’t see how it’s even possible for Ichigo to be OOC for the way he acts in the manga. The term ‘OOC’ is generally reserved for when fans portray a character different to how they’re portrayed in canon, it’s not generally used to refer to how characters are actually portrayed in canon.
You can argue that the canon portrayal of a character is OOC if the writer has been inconsistent with character development (or has had too sudden character development), but you can’t argue that in this case because Ichigo’s tendency to be polite and not-an-asshole to Orihime has been the case from the very beginning of the manga. It’s the exact opposite of OOC-ness: it’s in-character for Ichigo to act that way around Orihime.
He’s not an asshole to Orihime simply because she doesn’t annoy him. Ichigo doesn’t act like an angry lil’ cat just for the hell of it; he acts that way because he’s a very irritable and prickly person. he’s like a cactus. And if someone annoys him (which is easy to do), he gets cross. And we rarely see him get cross around Orihime because, amazingly, she rarely annoys him or makes him angry. She’s sweet to him and he’s sweet in return.
Note that I said ‘rarely’, not ‘never’, because, funny thing:
Here we have Ichigo telling Orihime she talks too much; he’s irritable because she annoyed (embarrassed?) him with that comment.
And here we have Ichigo calling Orihime an idiot. The whole premise of claiming Ichigo is OOC around Orihime lies in arguing that he’s not comfortable to be an asshole to Orihime, and yet here he is, calling her an idiot. (lol though it’s cute that the rudest he’s been to Orihime is when she wasn’t doing anything to annoy him, he was just worried about her. Oh, Ichi, your soft spot is showing (◡‿◡✿) )
All of this proves that Ichigo is capable of being his moody, rude, cantankerous self around Orihime. Like even with this ridiculous argument as a basis, you still can’t argue he’s OOC around her; not when it’s there, in black and white, in the manga, that Ichigo has acted like a ‘rude little shit’ to her on a few occasions, saying what he wants to say without filter. And Orihime is still cool with him after that, she doesn’t even blink, because hey! they’re comfortable enough around each other for this kind of banter!
So the idea that he’s not comfortable to be himself around Orihime = completely wrong. It just so happens that she very, very rarely angers him, and so there are only two occasions in almost 600 chapters where it can be said that he’s being rude to Orihime. Enough to completely hulk-smash the ridiculous argument that he’s not comfortable with her to pieces, but also rare enough to make you wonder that if he’s not “”“”OOC”“” around her, then why is it so rare to see him act like a grumpy old man around her? Why do we see his soft side around her so much?
Whether it’s because she doesn’t do things that annoy him or because he has a soft spot for her is up to interpretation. I think it’s a mixture. On the one hand, he has burst a few blood vessels because of her, but on the other hand, Orihime fusses over his hair, says silly things all the time, screeches ‘HI KUROSAKI-KUN!!’ at the top of her lungs every time she sees him, bursts into his room without invitation… and none of that bothers him. She’s this huge, loud hurricane, but she manages to navigate her way around him without ruffling his feathers. Incredible.
Aaaand just for fun, because the argument that Ichigo isn’t comfortable enough to be himself around Orihime is just so wrong:
Here we have Ichigo being blunt enough to talk smack about her bread - even though he’s apparently not comfortable around her? lol ok. Oh and even though this is a repeat of a conversation they had earlier in which Orihime grew irritated with him for saying the same thing. He knows that she’ll get annoyed, he knows she’ll sass him, (he also knows it is delicious, bwahahaha,) but he does it again anyway. If he was so uncomfortable around her, wouldn’t he… not do that??? (Answer: he’s teasing her. Not something you can do when you’re not comfortable with someone.)
And oh look!
Ichigo being tactless and speaking without filter around Orihime. If he was soooo uncomfortable around her and so awkward around her and so unable to speak his mind, why is he??? speaking his mind???
(Fun fact: one time Ichigo WAS unable to speak his mind around Orihime
he got told for being a coward and not saying what he honestly thought. #fukcing told)