Tomura Shigaraki has had cystic fibrosis since he was born. He has had many surgeries and chemotherapy appointments since then, but nothing seems to work.
Now, at age 21, he is almost always bedridden. When he isn't stuck in bed, he’s in a wheelchair, since walking winds him, and he’s just so weak. On the rare occasion that Shigaraki is allowed out of the house (with his adoptive father’s [kuriguri] supervision) he meets Dabi in the mall. The two exchange numbers and get to know each other before he has to go home.
Over the next 18 months, they get to know each other, hanging out at Shigaraki’s house, and outside. Meeting Dabi, starts to heal his depression. But slowly, the two realize they have fallen for each other..
In this, Kurogiri adopted Shigaraki and Toga when they were both baby’s. Giri is older in this, while everyone else is the same age as they are in the anime.