After going through all of this in one sitting, I must say I'm mixed
I suppose it's realistic that we all, like Sekine, will continue to carry our own personal mental baggage that we will probably never unpack properly
We also can pine for others and never have our feelings reciprocated, and we will have to live with that
That being said, as far as a story in a manga goes, I feel incredibly unsatisfied at the end of this. Seikine's trauma turned out to be a backdrop, a cause for the kind of character he is, rather than an obstacle he had to properly overcome (maybe with the help of opening up to others, maybe by his own willpower)
With only a single chapter to properly conclude all of this, he basically comes onto "The Grandaughter", she lets him this time, and they become a thing.
We'll never know if they'll ever properly communicate what goes through their heads (which I feel is a big part of what made this story compelling)
We'll never know if Sekine will stop being catcalled or harassed by people he had no interest in (or if he ever came to realize why these things happen to him at all, not that it's really his fault)
We'll never know if he ever actually comes to building an actual relationship and bond with his two "friends"
We'll never know if he ever gets to play his magic card tricks
And I suppose these plot threads being left unwoven is realistc to some degree
Doesn't mean I have to like it though