This manga really is a piece of art by itself, the story opens up with the MC being depressed and stoic but as the story progress this slowly changes as his promise was slowly being fufilled, the character development in this story is top-notch so I would do it a displeasure to try to sum it in a few words, although the fight scenes and the story at the start may feel repetitive we also see character development of the characters around the MC developing too and slowly relying on him, this story is really an emotional rollercoaster especially at the end where there isa bittersweet ending that although we could expect from the last few chapters but it still hits hard as one of the most memorable endings for me, I dont think there is anyway that the ending could be better, the artist and author also posted small side arts that really shows how things changed from the start to the end.
I highly recommend this as it is one of a kind and a must read for its unique plot and beautiful art