|Appearance||Period 41: The Erasing Blackboard|
Isaka has short, slightly messy hair with several loose strands sticking out. His bangs are split down the middle and frame his upper face. He has big, friendly slanted eyes.
A sporty and friendly classmate, Isaka is shown to enjoy playing basketball and has many friends- including Sari, who he appears to be close with due to their long-time friendship. He gets flustered when others tease them about their relationship, and its implied that he returns her feelings.
Isaka first appears during Kaori's time observing him from the classroom window, playing basketball outside during a free period. Kaori and her friends fawn over him, but once Sari shows up to join them she gets depressed again, seeing how much fun they have.
After Kaori discovers the legend of the blackboard to be true, she is surprised to find out that Isaka also hates tomato, like she does. It was this realization that caused her to decide to use the board in order to make others happy.
This was short-lived after she witnessed him mistakenly believe that Sari must have played a part in the good things happening lately. As everyone began to shower her with praise, Isaka was teased by his friend Yamaguchi, who claimed that it was Isaka who was especially appreciative for her being there. When Kaori angrily ran back to the blackboard to rid of Sari, she thought about the discussion she overheard them have, in which Sari questioned their relationship and wondered if he liked her romantically. He grew quiet and bashful, affirming Kaori's concerns.
Once break ended and everyone returned to class, Isaka and everyone else were alarmed to find out Sari had gone missing. They wondered what could have possibly happened because it's not like her to suddenly take off during the middle of the school day. Kaori feels no sympathy though, and she approaches Isaka to ask if she could play with him and his friends to take the missing girls place when they play. His friend refuses since she isn't any good at sports, but he chastises him and agrees.
However, once school ends, he happens to notice Kaori sneak through a nearby building window and grows suspicious. He would end up following her there, and as soon as she begins to write down another girls name, he suddenly stops her. He mentions being told the rumor by his sister, then yells at her for what she's done, angered that someone would do something like this. Kaori, aware that he probably hates her now is unable to bear with it and runs away to hide as he contacts a Teacher. Kaori returns and runs past them realizing she has to do something to avoid getting into trouble -and to avoid being erased by someone holding a grudge- and she locks herself in the room.
Seconds pass, and suddenly, Isaka and the Teacher get the door open. They see Kaori is now missing, with only her eraser and chalk left behind.