I really liked the nebulous feeling this manga's conflict gave me. On the one hand, tattoo girl has the right to get whatever tattoo she likes. In contrast to something like buying a car, or taking a new job, or most other big life decisions, getting a small tattoo really only impacts her. It doesn't affect the relationship financially or logistically. But relationships are complex, and in practice I think I would be just as upset as long haired girl, and for much the same reason. I wouldn't be bothered by the tattoo as much as what it says about my partner's decision making process. Either they are so impulsive that they would make a life-long decision without me, or they value my opinion so little they didn't bother to ask. Either way I'd feel really uncertain about my future with that person, and I think this manga captured that feeling well.
I'm less thrilled with how this manga resolves the conflict. To begin with that "say you like it" bit annoyed me. If you wanted her to like it you should have asked her ahead of time... :/ I get what the author is going for here: long haired girl's issue was that it felt like tattoo girl didn't care about her, and tattoo girl was comforting her by telling her she was thinking of her. But I think the dialogue needed to be worded better. What irritates me most though is that tattoo girl is smiling throughout the whole conversation. Like we have long haired girl upset and talking about how she didn't feel valued, and tattoo girl is grinning??? Why? It makes her apology seem insincere.
I do like the thing at the end with the sleepy face though. It illustrates one reason why its good to talk to your partner about your life decisions, even if it doesn't technically impact them: they might have good advice. In this case, I think the sleepy face would have been a way nicer tattoo, and tattoo girl seems to agree. Overall I'm happy I read this story, since the conflict was really interesting, even if I didn't completely agree with how it was resolved.