A first year student in Course 2 of the First High School. He is the eldest son of Four Leaves Technology (FLT) company's president, part of the Yotsuba clan. His only sibling is Shiba Miyuki. Since he was born in April and Miyuki born in March, they are studying in the same year according to Japanese school system. Miyuki scores at the top of the class of freshmen, while Tatsuya scores near the bottom in the technical skills portion. The school is split between the high scoring students, blooms, and the low scoring students, weeds. Tatsuya appears to have a very cold personality except when it comes to his sister and his friends.