Kokoro Connect Light Novel Volume 03

Kokoro Connect Kako Random (ココロコネクトカコランダム) is a Japanese light novel written by Sadanatsu Anda, with illustrations by Shiromizakana. Volume 3 was released on September 30, 2010. Kako Random was adapted into Anime Episodes 11 to 13.

Summary
Student Cultural Society, more like Babysitter's Club!

Winter break is here, and it's nearly time for New Year's festivities... but there is a new troublemaker in town, and its name is "The Second". This time, the members of the Student Cultural Society - minus Taichi - are chosen at random to physically regress into younger versions of themselves from 12 PM to 5 PM every day! Tensions build as old, painful memories come to light. Meanwhile, Taichi is forced to keep quiet about "The Second" or else it threatens to make things even worse... Can they last until the clock runs out?

Trivia

 * "Kako" (過去) translates to "Past."
 * This volume has the most major changes between the novel and anime versions.