Hansuke Doi is a tall, young teacher at Ninjutsu Academy, known for his striking appearance and quirky habits. As the homeroom teacher of Class 1-Ha and the advisor of the Gunpowder Committee, he deeply cares for his troublesome students, despite always being stressed by their antics and the principal’s random ideas. With a hidden tragic past as a noble’s child-turned-ninja, and a special bond with Kirimaru, he’s both a skilled ninja and a lovable mess, admired by students and viewers alike.
Hansuke Doi is 175 cm tall, which is quite tall compared to the average man in the Muromachi period (about 156-157 cm).
He is considered “the most handsome at the academy” and is recognized as an attractive character.
His clothes in the original story are often dirty, because he rarely has time to wash or change outfits.
His hair is quite damaged with split ends, and even Takamaru Saitou, whose family is in the hairdressing business, once got angry at him for not taking care of it.
Despite his rough look, he unexpectedly became the face of a beauty and hair product campaign in 2025.
Hansuke Doi cares deeply for his students in Class 1-Ha.
He is patient and committed, even though the students struggle to remember lessons and often cause trouble.
He is stressed by constant supplementary classes and make-up exams, and by the principal canceling classes with sudden ideas—this made him develop stress-induced gastritis.
Still, he always calls his students “good kids” with affection and values them above all.
He is dedicated but has low living skills; his home was a messy room before Kirimaru moved in.
Hansuke Doi has a hard time getting household chores done and forgets things like trash duty or rent payments.
He also struggles with relationships, never having a girlfriend and being described as a “fighting daycare worker” by the creator.
Hansuke Doi was born in Fukuhara, a part of modern-day Kobe, and was once from a powerful family.
His family was attacked and lost everything when he was a child, leaving him orphaned.
He became a monk, learned military strategy and ninjutsu during his training.
He failed a mission at age 19 and met the Yamada family after being rescued by Denzou Yamada and his family.
He couldn’t give out his real name when he started teaching at the academy since he was still on the run as a rogue ninja, so he was called “Hansuke” (meaning “half-done”) as given by Denzou Yamada.
His connection to the Yamada family led to his becoming a teacher at the academy.
He has been compared to Hounen, a famous historical figure, for his background.
Hansuke Doi is an expert in gunpowder and military strategy.
However, he sometimes mixes up gunpowder ingredients and causes accidents.
He claims he is not good at throwing shuriken, but he has perfect aim with chalk.
He often uses classroom items like the attendance book, chalk, and blackboard erasers as weapons.
He can also use kunai and swords when really needed.
He has a special talent for understanding nonsense or decoding many students talking at once.
His attendance book is reinforced with steel so it can be used as a weapon or shield.
With Students
He struggles most with Rantarou Inadera, Kirimaru Settsuno, and Shinbei Fukutomi, the trio who always get into trouble.
Despite their antics, Hansuke Doi cares for all his students and earns their respect in return.
With Kirimaru Settsuno
He has a deep, almost family-like bond with Kirimaru, who also lost his family in war.
Kirimaru lives with him during school breaks, and neighbors sometimes think they are family.
Hansuke Doi’s past makes him especially sympathetic to Kirimaru’s struggles.
Sometimes Kirimaru makes Doi do all his part-time jobs, turning Doi into an expert babysitter and laundry worker.
With Colleagues
He is the youngest teacher at Ninjutsu Academy and is respectful to the older teachers.
He will fight back if anyone mocks his class, showing his pride.
He works closely with Denzou Yamada, who named him “Hansuke” and is like a mentor.
Yamada’s son, Rikichi, thinks of Hansuke Doi as an older brother.
With Neighbors
Hansuke Doi often misses chores and rent because of his busy life at the academy.
His neighbors and landlord sometimes think he moved away, but they still care for him and Kirimaru.
Rival
Moromizumi Sonamon, a rival ninja, once lost to Doi and now considers Doi his rival, often showing up to challenge him.
Other Relationships
He befriended Ishikawa Goemon during his training days (anime only), a famous legendary ninja who traveled overseas.
Hansuke Doi hates food made from fish paste, like fish cakes and chikuwa, and he tries to make Kirimaru eat them for him.
He has a psychological trauma from a story about someone choking to death on chikuwa, but his excuse changes every time.
The Past Revealed
In the 50th volume and anime episode “Hansuke Doi and Kirimaru’s Episode,” Hansuke Doi’s noble origins and tragic childhood are revealed, confirming his orphan status and difficult past.
Meeting the Yamada Family
At 19, while escaping after failing a ninja mission, Doi fell and was rescued by Denzou Yamada’s family on a trip.
Yamada’s wife noticed Doi’s potential as a teacher and convinced her husband to help him join the academy staff.
When he first started teaching, Doi was so nervous that he barely spoke and was just called “the young man.”
He was officially named “Hansuke” because he couldn’t reveal his true name.
Connection with Kirimaru
Doi allows Kirimaru to live with him during school breaks because their backgrounds are so similar.
He supports Kirimaru as more than just a teacher, forming a unique family bond.
Teaching Trouble
Doi often has to cover for his students’ accidents, slow learning, and make time for extra lessons.
He uses unique methods in class, like using whatever tools he has for ninja training.
He gets angry with the principal or other teachers but is always patient with his own students.
Rival Encounters
Moromizumi Sonamon often challenges Doi, but Doi always uses simple items like chalk or his attendance book to win.
Popularity and Anime Moments
Hansuke Doi is extremely popular among fans, winning first place in a major anime character poll and getting dedicated episodes about his life and relationships.
Hansuke Doi uses “watashi” as his personal pronoun, but in early anime episodes he used “ore.”
He sometimes appears dressed as “Hansuko” (female version), and surprisingly, he looks good in women’s clothes.
He is so popular that fans sometimes confuse him with another famous chef named Doi.
His famous phrase “I taught you this before!” is borrowed from Denzou Yamada.
There is a running joke about how he manages to hide all his hair under his hat or hood.
His attendance book is reinforced so it can double as a weapon or shield.
Hansuke Doi’s house is often assumed to be empty by his landlord due to his absence.
“I’ve taught you this already!”
“Remember, a ninja makes use of whatever he has.”
“You’re all good kids, even if you’re a little slow sometimes.”
When dressed as a woman for school events or due to Denzou Yamada’s schemes, his “Hansuko” persona even gets praise from characters’ parents and school staff.
He appears in musicals as Hansuko as well.
Due to living with Kirimaru, he became very good at babysitting and laundry.
He is often called “the first love thief” by female fans because so many students and viewers admire him.
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