Three friends that all do art together, trying their hardest, but as the story progresses, the narrator begins to think that life isn't worth it and he doesn't need to try hard anymore.
I am a nihilist, so I'm definitely biased when it comes to the topic of nihilism and the ultimate meaninglessness of life. And I don't care for how this manga relegated nihilism to an uncool, hedonistic phase which should be moved on from, and implies that the only way to care about others or have a sense of responsibility is if you reject nihilism. That is simply untrue. A nihilist recognizes that everything we do is meaningless once we die, and it's true that that does indeed spur the nihilist into living the way which fe wants to rather than trying to conform to some standard which others think we are supposed to live by. But where this manga mischaracterizes nihilists is that it implies that "living the way you want to" means living selfishly. Many (if not most) nihilists still find enjoyment from interpersonal relationships and human connection, so why would they want to live in a way which damaged those types of things? Ao clearly sees living while caring for others, while sticking to your principles, and while putting effort into things as a "cool" way to live. So if fe finds that "cool," clearly that would be the way which Ao would want to live. And choosing to live while having goals and while taking those goals seriously doesn't make your life any more or less meaningful as anybody else's. Nothing makes any life more meaningful, or somehow a "better life." You can live in whatever way you want--even striving for goals with great effort and determination--while acknowledging that your actions aren't making your life more worthwhile or something, that your life is still meaningless. But that's not how this manga chose to end things. Instead, it showed Ao realizing that fe had been on a path that would've squandered this one life which fe was given and implies that fe has now found meaning in life and has discarded the notion that life is meaningless. Discarding nihilism is never a happy ending in my book. But, again, I'm biased on that topic.