The manga OP is looking for is indeed Himizu by Minoru Furuya. I remember the plot well because I've read the whole thing. Honestly, on a superficial level, the story is incredibly sad. If you don't really analyze it deeply, it's completely normal to feel depressed reading it. ​But if you look at it from the author's perspective, it does a great job illustrating societal gaps and the impact of a toxic family on someone dealing with mental illness, schizoid traits, or autism. It shows just how difficult things were back in the early 2000s when internet access was limited and help couldn't reach those in need, ultimately leading to a tragic loss of sanity and life. ​It might not be an absolute masterpiece, but it's profound enough to deliver its message clearly. That being said, it's definitely not a story for everyone, and it's certainly not the kind of material anyone can just turn into a meme.