This is a very nuanced manga. Not everyone will be able to appreciate its genuine sincerity, and it doesn't pull any punches.
Characters - 9.5/10
They're all just so well written. I feel like there's a little something missing, though. The character designs are iconic, and, dare I say, might set a standard for future mangaka to aspire to.
Art - 10/10
What else can I say? Ishida Sui is the artist, and it carries all the gritty charm and detail that Tokyo Ghoul did. Stunning backgrounds and well defined characters make it pop. The page layout is simply extraordinary, it flows like something out of Akira Toriyama's golden days.
Story - 10/10
Absolute perfection. It's extremely subtle, but the premise and opening chapter echo throughout this masterpiece. In this day and age of Isekai-manga-that-didn't-need-to-be-Isekai, having a manga that follows through on the premise, and doesn't forget its roots. Not to mention the character motivations and development is top notch.