Ergh, for people that like spoilers about Kuzu no Honkai (regarding Ecchan and Hanabi):
To be honest, I'm not quite clear on the main story, but I believe Hanabi had her heart basically broken by her real love (sensei) and Mugi. The side story between Ecchan and Hanabi basically starts with Ecchan taking advantage of Hanabi's vulnerable state to mend her broken heart. They get it on, but both girls know perfectly well their relationship isn't stable and won't stay because Hanabi doesn't love Ecchan the way she loves her.
The two girls go on some sort of vacation where Ecchan's cousin is staying (and he's hinted to be romantically attracted to Ecchan, but he's a good guy and knows she likes Hanabi), where Ecchan is determined to shut things down because at this point, Hanabi isn't openly accepting the fact that their relationship is not meant to be. Ecchan takes the opportunity to enjoy their last moments together because she knows after this experience, they won't be able to go back to being best friends.
However, Hanabi tries to push the relationship a bit further, but we see it's most likely not out of true love - whatever it is, they're just not on the same page. Ecchan decides she can't take it further and they have an argument under the rain, where Ecchan tries to sever the ties between them. Hanabi desperately tries to remain as friends, but Ecchan is having none of it, telling Hanabi that it's too painful for her. They apologize over the one-night stand, where Ecchan believes herself to be a scumbag for taking advantage of Hanabi, whereas Hanabi is equally disappointed in herself for letting it happen despite being fully aware of where Ecchan's feelings lie.
After more bickering, Ecchan sees in Hanabi's eyes that she is truly not willing to let Ecchan go as a best friend (because she doesn't want Ecchan to be lonely), so I believe they decide here that it's for the best if they remain distant from one another for a while until the dust settles. They do love each other, but it's clearly too vague to determine where their current relationship stands. Most likely, they will return to their "best friends" status, but it's possible that they'll never talk to each other again. The least likely to happen, imo, is them getting together, but I guess it's not impossible either. In any case, Ecchan hints here that she may consider opening up to her cousin more, sooo...
