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

Rainy weather sends the bored ninjas to search for the Loch Ness Monster in their pond; ninja-master Onsokumaru and a masked Sasuke keep a close eye on a girl-girl dating spectacle.

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.

Onsokumaru is sent to Hell and encounters demon schoolgirls, demon wives, and demon in-laws; when it's too hot to train, the ninjas plan a Summer Festival to brighten the mood.

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.