The spellbook he was supposed to study had become so uninteresting the second he saw you, sitting on a bench, impatiently swinging one leg with your arms crossed and a sour expression. He could almost guess why, but it irritated him more than he let on.
Remus wasn't the back-stabber type, he wasn't trying to go after the same person as James, not at all, however if they were talking about facts: he saw you first. In that Defense Against the Dark Arts class in third year, when you got scared by your own boggart and hid behind him, so he cast Riddikulus for you. He remembered it so well, all of it.
But, he failed to make it clear that he liked you for the past four years and... That led to the present, when he had to swallow the lump in his throat every time James referred to you as his. What could he do? He was fully aware that he had nothing that James had.
Personality? No, cunning? No, beauty? No, agility? No, smooth talk? He doesn't even want to get into that topic. A Potter was a Potter, a strong surname that guaranteed him a certain respect in the halls of Hogwarts, on the other hand, Lupin was nothing more than a shy boy hiding a dirty secret, no backstory, just scars.
Sirius had tried to lighten his mood the last few days, telling him that James wasn't taking it so seriously, that he'd find someone else soon and the path would be clear again. But, honestly, he was shaking with jealousy just thinking about you kissing someone out there, even if that someone was one of his best friends who never knew he had feelings for you.
Idiocy, that's what it was, he shouldn't be so jealous of someone he never had, he should be happy that his friend was happy, he wasn't.
The urge to threw up that was growing in his stomach only increased when he saw James sitting next to you and he didn't want to, but he couldn't help but feel it. He felt so stupid for not saying anything, expecting you to notice the way he was always there, offering what he could without you even asking for anything.
When your gaze landed on him across the hall, he raised the book in front of his face again. Nothing happened. “Remus?” Your sweet voice made him sigh, lowering the book to look at you with big, dark eyes that seemed to ask you: What do you want?
“I want to go watch Quidditch practice, but well... I didn't want to be alone, can you go with me?” He could have said no, because he knew you just wanted to go and see James flying back and forth, but he couldn't deny you anything you asked, not even if he wanted to.
Without answering you properly, Remus stood up from the bench he was on, looking at James behind you before turning his eyes back to your face. “Okay, go ahead... I'll meet you there.” Truth be told, he just didn't want to seem like the third wheel by going with you and your... almost boyfriend to the Quidditch pitch.
He waited for you to walk away a bit before he started walking. Just adding one more thing to his list of comparisons: he didn't play Quidditch like James either—though he was a great flyer and really enjoyed watching the matches, he didn't want to get involved in that, especially when lycanthropy left clear marks on his agility after nights with a full moon.