Ninja trainee Shinobu goes on a mission for her perverted headmaster to collect underwear from high school girls, first targeting Kaede Shiranui.

Onsokumaru gets angry at Shinobu's little sister, Miyabi and decides it's time for a little one-on-one; Shinobu is kicked out of the manor, and heads to Kaede's family.

Rising temperatures give Onsokumaru a perfect opportunity to get Shinobu and Kaede into their swimsuits; Miyabi has a crush and uses the Ninja Pharmaceutical Group's special love potion to help things along.

With Shinobu stuck at Kaede's house as a typhoon looms, those left at the ninja manor witness Onsokumaru's darkest hour; when Onsokumaru offers his wisdom to a mushroom picking expedition, the ninjas are in for a magical ride.