Ken-chan

A drawing of a much younger Dr. Tenma from back when he was in middle school and on the Track and Field team. He’s probably 13-14 here? It's about... the early to mid-70s here.

This probably won't make sense unless you've read the supplement to Monster, Another Monster. Here are relevant parts describing this (the author of the book is interviewing people who knew Tenma back in Japan):

"One year after their marriage, Kenzo was born, a very bright boy who needed little outside assistance. He attended nearby municipal elementary and middle schools, scored some of the highest marks in the city, enjoyed music and art, and was a member of the track and field team."

"I bet nobody else remembers that he set a short-distance running record in middle school while on the track team. He was very good at solo sports."

"On the track team after school he would always strain so hard to pull ahead so that he was running alone."