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Rizu is a short but well-endowed girl who wears glasses. Rizu has light brown hair and blue eyes. She is very short at 143 cm (4 feet 8 inches), yet has the biggest bust size among the female protagonists at F cup, and possibly G when she measured it again in chapter 44. She becomes an H cup by the time she reaches freshman year at college.
She wears a school uniform which is a half-sleeved or a long-sleeved depending on the seasons, informal styles. At home when she's working, she wears kimono working attire with an apron that says Ogata Udon. Her arms are extremely thin, long, and soft as well, as she seems to lack any apparent muscle tone; which is probably why she doesn't normally wear sleeveless clothing.
Rizu although she is seen to always have a poker face on, she's capable of showing emotions whenever she's happy or down. A math and science genius since young, she is known as the "clockwork Thumbelina". However, she isn't good at reading people's feelings and emotions, thus failing her humanities and not recognizing that she is in love with Nariyuki. From the time she was young she was never satisfied with a vague answer, which she finds humans emotion to be incomprehensible as compared to mathematics or science, and is oblivious to her surroundings once she's focused on something.
Rizu is also demure, even though she says she doesn't believe in superstitious beings, she got scared easily when she watched a horror movie by herself. She also tends to misunderstand things a lot as seen in Question 37 and Question 44.
She is a very serious girl, always wants to understand human behaviors, especially love issues, by scientific methods. She is extremely determined, and sometimes stubborn, to attain psychology in university, although the reasons had been changed in later chapters.
She is poor in interpersonal relationships, sometimes difficult to express appreciation to close friends such as Sawako Sekijou.
She is highly influenced by her grandmother, who died in her childhood. She once misunderstood that she was hated by grandmother as she relied on her grandmother so much. She finally understood her grandmother and played games with her own friends in Question 117.
- "Next time...I want to make Yuiga-san 'delighted'. Not with something weird, but by delivering results," - Rizu Ogata, Question 44. 
- She is shown to be very bad at games, losing to everyone every time.
- She was Nariyuki's first kiss and vice versa, though by accident.
- She knows Fumino before the story starts.
- She calls "Yuiga-san" in early chapters, and then "Nariyuki-san" in recent chapters.
- She has not grown any taller ever since elementary school, always staying at 143cm.
- She always eats udon on studying.
- She has very serious nearsightedness, and cannot see without glasses.
- She was also shown to wear contacts, as she is wearing them after getting a makeover.
- She has a bust size of 91 centimetres; by her freshman year in college, her bust size has become H cup. This also mean she has the largest known breast in the series.
- Names of her parents are not revealed yet.
- Question 44