Sho, a high school student preparing for college entrance exams, receives a sudden call. The caller is Ran, his childhood friend who used to live next door. She's also currently a re-taker and asks to stay at Sho's place during the winter cram school session. Reunited after a long time, Ran still retains her old charm, but her stunningly developed breasts, which have grown to an unbelievable size, are beyond anything Sho could have imagined from their past playful teasing. Their intimate and sweet, yet slightly tart, sex-filled life together begins as Ran, in her casual, revealing attire, seductively flaunts her ample bosom.