Shinjo Serina

She is the younger sister of Haruna, who is also a childhood friend of Masato. Contrary to her brainy older sister, she is not very smart. But she is the type of person who follows the saying, “If it takes a long time to do it right, do it fast.

In a different way from her older sister, she is popular for her body shape which is visible even through her clothes. She is not as sly as her older sister, but she is clearly a strong woman.

Although she is not as mean-spirited as her older sister, she is very aggressive toward Masato, whom she clearly disrespects. She is determined to earn money by having fun, which is why she refuses to tutor Masato.