The Soichi stories are among my least favorite Junji Ito works. They’re fine, they certainly have his excellent art style, but the main character is just too weird to like. Soichi is a strange member of an overly-indulgent family, chewing on nails and trying literally to curse his siblings. That’s weird. Just generally unpleasant. We’re not really supposed to sympathize with Soichi, but even with him not being explicitly a good guy it’s unpleasant to spend time with Soichi as the main character.
Part of me wonders if Soichi is a semi-autobiographical Junji Ito story. He’s drawn himself before and there are similarities to the tongue in cheek style he uses for himself. That being said, I doubt that Ito was cursing his siblings and forming gigantic spider costumes to terrorize the neighbor kids. Each of the stories in this book is a little vignette of Soichi being certain he’s the only real person in his school, like a good psychopath, followed by him playing with some malign force or another to curse them. My favorite is probably the one in which Soichi’s brother has a carpenter soundproof his room, only for Soichi to sabotage the effort, climb between the soundproofed walls, and torment him with noises until he runs out of oxygen and passes out. There is always a moral comeuppance in this stories for Soichi, by the way.
The usual endorsement: read Soichi if you like Junji Ito. The style is here.