Compelling characters and lovely art make Lucky-kun a pleasant, if sometimes restless voyage into the only-slightly-quiet life of stepbrothers Mura-chan and Subaru-kun. From estranged "brothers" to disquiet presences in each other's lives and then again to gentle, if passionate, lovers, they will reveal the best and the worst about themselves, in a way that is both calm and pervasive.
Yes, the ending is terrible, but not for the reasons named in previous comments (in my opinion of course). I don't usually read tags beforehand because I don't want to be spoiled. That being said, I can't say I wasn't expecting a sad ending. To be honest, the clues were there throughout the story. However, the grand finale that those clues were amounting to did not come to fruition. Spoilers ahead.
Remember when
Subaru mentions the short story book Mura took from his bookshelf? When, with melancholy eyes, he remembers the birds threw themselves into the sea and drowned?
And then, how it was a matter of discord between them who would leave who behind. They are young, they are fearful and anxious of the future, I get that. But on a more metaphorical level, I thought it one of those apparently "superficial" subjects that come to bite us in the arse once tragedy strikes or something. Subaru is a dramatic character, so I was sure the author would cook something out with it.
The way their romance was construed, it was meant for a great ending. I had perhaps too high expectations, so the actual ending just seemed bland and rushed and not worthy of the characters.
Ultimately I think I would like to reread this some day, but hopefully I'll remember to skip the last volume/chapter.
Character-wise + art: 8 out 10.