juno and arthur used to be lovers when arthur was still a freshman. they met from tinder. arthur didn't really expect much from their first meeting, but juno actually contacted him back and said that she wants to get close with him. it was quite suspicious to arthur on how easy that was, but arthur gave in and told himself that this going to be a new adventure to him. their relationship lasted for two brisk months. the beginning of their relationship is smooth-sailing interactions, they used to go on drive trips and arthur would take juno to places he thought juno would liked. after a few weeks, their relationship get caught by leo and they decided to come out clean. they were an okay-ish lovers and doesn't have much conflicts about their relationship, but they weren't really at the stage of loving couple as juno wasnt really emotionally opening up to him and arthur was worried if he didn't take care of their relationship well. but they hit it off really well in the sheets. until one day, juno suddenly told him that she only want them to be friends with benefit (she didn't actually said the exact words, but you get the point). she told him that she did fall for him, and she thanked him for trying to make her happy and that she enjoyed their moments together but she just fell out of love naturally. yet, she did enjoy getting physical in bed with him. this relevation was out of what arthur would've expected, he was very taken aback and was very confused on what to answer. probably because it was the mood of the diner, he said yes. they continued being casual partners for 2 weeks, before arthur realizing that this will just mess his still-not-gone feelings for juno, and that if this continue, he will hurt himself and probably juno too. he knew that he can't force juno's feelings, so he braved himself and talked to juno that he would like to stop because this is not just his thing. he apologized too many times, that juno had to stop him because he was making her feel like the jerk. 

of course, arthur still has some feelings left that time, but seeing juno moved on like it was nothing, he felt like it's time for him too. it took a while, but he did it. they started becoming friends again thanks to leo. now they can joke about it with the others, saying how naive they were and all that jazz, a lot of with leo's clowning them. arthur swore he doesn't have feelings left for juno now, but every time it's only the two of them, he can't never get rid of the awkward air between them. arthur have always want to make their friendship going, and be all casual, just like with others. but somehow, it never really went that way with juno and him. it felt like he was the one who's holding back himself, which is.. very rare of him.