Tadashi is the youngest of ten. And has nine older sisters, which was more than interesting for him. His parents weren't always able to support them all emotionally, since there was so many of them, and so little time to be there for all ten of them. And most of his sisters are older then him, so really he's only close with a few of his sisters due to age difference.
He still talks with them, he just isn't as close to them as he is with his sisters Ryoba, Megami and Mai.

When he was three, he met two kids named Connor Murphy, and a popular superstar that SpamChan forgot the name of.

The three of them, were inseparable. They became the brothers that Tadashi didn't have before growing up. They were known as The Three Musketeers at school, and did a play.

Tadashi: If I'm being honest, I wanted to be in the play so that I could wear the big hat with a feather.

At about eleven years old, he had noticed that Connor had been having a hard time. Normally, they would be all energetic with one another and go to his house to watch stuff his parents wouldn't let him cause they're superstitious about certain things.

One day, Tadashi came over to pick him up from school, and he hadn't bothered to knock cause they knew each other for so long. He couldn't find him, when he went to his room, he saw Connor's unconscious body with a cutting knife and slit wrists.

Both he and his other best friend had a hard time with it, but Tadashi took it the hardest. He couldn't help but feel anxious every time he thought about it. And one day, one of his older cousins had offered him heroin, and he had taken it not knowing what it was. He was eleven, and grieving. His cousin told him it would make him feel better and sent him with a package of needles and showed him how to use it. He was also given another kind of drug, but didn't remember the name of it.

He kept the heroin a secret from his sisters and parents for about a year. But, come around the anniversary of Connor's suicide, the twelve year old was really anxious and he had overdosed in the bathroom from the heroin.

His sister, Megami had been the one to find him and find him unconscious on the floor with needles everywhere. He had been quickly taken to the hospital by their uncle Hizashi who had been watching them, and he had almost died in the ambulance.

Until the age of fifteen, he had been taken to therapy and rehab to deal with his addiction before his other best friend was moved and he was alone and anxious, and when he was anxious he got drug cravings and he got antsy and depressed.

When he was invited to a pizza party thing at one of his old friend's church, he had gone and he learned about God and Jesus and he had started to go there.

When he got out of rehab, he was able to join Class 1C in UA High School and he met someone from Class 1A named Mina Ashido, and they had grown to like each other and they soon started dating.