Seiji Sanada, a nearly 30-year-old corporate drone, woke up one morning to find that he'd been sent back in time to the spring of his sophomore year of high school. Seiji had long regretted graduating without confessing to his beloved world history teacher, Haruka Hiiragi. So this time, he decides to tell her his true feelings...and she's surprisingly okay with it?! The two of them began discretely dating and their life as a couple was bliss... but Hiiragi-sensei is a woman so sweet, she’ll spoil her man rotten! A super flirtatious and rosy school life begins!