The story follows Hanawa sensei and what he does in the sidelines throughout the parent series' timeline.

Hanawa sensei was a really good part of the original series as a character because he really bridged the Kotaro's two worlds (school life and life at Shimizu apartments) together. So it was interesting to see his personality and home life(that was hinted at in the original series) fleshed out and emphasized. Hanawa sensei's nervous enthusiasm is a breath of fresh air, and seeing him struggle so hard to grow as a teacher really makes you root for him.

Anyone who was disappointed the characters at Shimizu kindergarten weren't given enough screen time is in for a treat.