Yakuzen Kusuri is a third-year high school student with a passion for chemistry that borders on obsession. As Rentarou Aijou’s fifth girlfriend, Kusuri brings her quirky energy and genius-level potion-making skills to the chaotic Rentarou Family. Due to an immortality experiment gone awry, Kusuri spends most of her time in the body of an eight-year-old, a stark contrast to her true teenage self. This duality makes her one of the most unique and hilarious members of the family.

Kusuri’s relentless enthusiasm for testing her experimental drugs often leads to comical and unpredictable situations. Her childlike appearance masks a brilliant mind and a heart full of love, making her an unforgettable addition to the Ecchiverse.

Personality & Appearance

Credits: Bibury Animation Studios

Kusuri is bubbly, energetic, and completely fearless when it comes to experimenting with her potions. She speaks in third-person and ends her sentences with the playful "-nanoda" (translated as "yep, yep"), a quirk she shares with her eccentric family. While her drug experiments often spiral into chaos, her genuine intentions and love for her friends shine through.

In her teenage form, Kusuri is a stunning young woman with long red hair tied in a ponytail, turquoise eyes, glasses, and a beauty mark on her chest. However, she is more commonly seen in her child form, where her smaller size and shorter hair make her look far younger than her actual age. This duality is a constant source of humor and surprise for those around her.

Powers & Abilities

Credits: Bibury Animation Studios

Kusuri’s unmatched chemistry skills make her an asset to the Rentarou Family—albeit an unpredictable one.

• Chemistry Mastery: Kusuri’s ability to create potions with a wide range of effects is unparalleled. From love potions to transformation elixirs, her concoctions are as miraculous as they are volatile.
• Dual-Form Transformation: Due to her self-administered immortality potion, Kusuri can alternate between her childlike and teenage forms, though she spends most of her time in the former.
• Ingenious Problem-Solving: Kusuri’s quick thinking and resourcefulness often save the day, whether it’s crafting an antidote or creating a potion to assist her friends.

Trivia

• Kusuri’s birthday, April 18, aligns with Japan’s Invention Day, reflecting her innovative spirit and love of chemistry.
• She has kissed Rentarou at least 42 times as of Chapter 188 and holds the record for the longest dream kiss sequence in Chapter 56.
• Kusuri’s antics often place her in the “straight man” role during comedic group interactions.
• Her love of potions draws comparisons to other alchemists in popular media, but her focus on chemistry sets her apart as uniquely scientific.
• Kusuri’s rivalry with her classmate Torotoro Kishika often results in hilarious spats, especially when they compete for Rentarou’s attention.
• Her transformation abilities draw inspiration from classic anime tropes but are uniquely tied to her potion-making expertise.