Beautifully written! I was really on edge the whole manga, scared of a tragic ending. Immortality truly is a very conflicting concept that seldom fails to make me emotional when it's subject of stories. Luckily, this has a great end - open to interpretation of what their distant future may look like, while simultaneously still ending on a hopeful and satisfying note (SPOILER: I was so glad MC decided to stay with the ML and accompany him together through the rest of both of their lives!!). Had to suppress my tears at the end haha! I'm glad they won't have to be alone ever again, as they will always have each other and now have their yokai friends as well! - I wish them all the happiness in the world.
Wadatsumi no Yometori