Natsuumi Manatsu is a part of the main cast and group leader of Tropical-Rouge! Precure, Precure's 18th season. Originating from Minamino Island, her main goals are to attend school at Aozora City where her mother resides, participate in school club activities, and overall do whatever's most important in the moment!

Upon her first days of touring the city, she meets Laura at a secluded beach, and immediately gets ecstatic to know she's befriended a real mermaid. Laura hands her the lipstick she dropped in the ocean on her ferry to the island, and as thanks Manatsu lets her try it on so she can get the same tropica-shiny feeling that she gets while wearing it. "Tropica-shine" in her words being, a burst of confidence that you can feel glowing from within you like the warm summer sun.

The two part for a while, until Manatsu hears that Laura is in trouble and rushes to her aid. It's with that boost of motivation and strong love for the connections she's made that she gains her Heart Kuru Ring and the ability to transform into the embodyment of joyful, everlasting summer, Cure Summer! Now unbreakable by the Yaraneeda's motivation-stealing power, she quickly apprehends the monster and saves Laura, who then agree to work together to find more Cures and form a team to save the world from the Witch of Delays's power.

Cure Summer's special attack is Otento Summer Strike, which ironically makes it's way into her image song OH! TEMPT SUMMER DAY (also the name of this listing), with the first part of the title "OH! TEMPT" being a homophone for "Otento" meaning "sunny".