I'm in Love and It's the End of the World 4

Ever since Mahiru’s new boyfriend, Aoi, lost his mother, he’s been looking after his brothers and sisters. Once she learns what life is really like for him, Mahiru tells herself she’s going to do everything she can to be the proper girlfriend he needs. But work keeps Aoi busy…and once Mahiru’s twin sister, Mayo, gets a job at the same café where Aoi works, they’re fast friends! Mahiru’s not happy about how well Mayo and Aoi are getting along…and just like that, Mayo and Aoi’s old friend, Ginga, find themselves in the middle of this gloomy-girl-meets-stubborn-boy story! The plot thickens in Volume 4 as a few big misunderstandings threaten to throw this fairytale romance off its tracks…