I have been reading a manga that has kept me on my toes from the first page. It is called With the Light - Raising an Autistic Child (Japanese Title: 光とともに…〜自閉症児を抱えて〜). There are 8 volumes in English (JPN release counted as 15 volumes, otherwise the same length), and I recently finished volume 3.
I will try my best to sell you on it without spoiling anything.
The story focuses on the Azuma family, who live somewhere in Japan (it might have said where at one point, but I forgot). They have a son named Hikaru, who shows signs fairly early on of something being off. He is eventually diagnosed with (IMO a severe form of) Autism, and a good chunk of the first volume is mostly spent focusing on the impact on the Azuma's from both a social perspective in wider Japanese society, and within the family (grandparents, in-laws, family drama, etc).
Despite all the challenges the Azuma family faces, and despite the shenanigans Hikaru will cause or otherwise be involved in (again, no spoilers), you can't help but cheer him on the entire time you are reading. You get to watch him grow as a person, along with everyone else around him. There is drama and suspense, there is a lot of wholesomeness, and is a well balanced slice-of-life.
That said (3rd time, no spoilers), the manga author died before they could finish the series, so even though I haven't read to the end yet, it is safe to say that it will end on a cliffhanger. Despite that, I still wholly recommend this manga, and will link it below for you to read for yourself.
Based on my prior research, that is what volume 8 (JPN volume 15) consists of. They were illustrations that were made prior to the author's death, between 2009 and 2010, which were gathered together and published as a single volume posthumously. So sadly, my last point still stands.
Beyond that, I don't know much else. It would probably require being fluent in Japanese in order to search for more information.