Aihara Kotoko (Sato Aiko), in 'F' class, is a direct contrast to Naoki in terms of studies, character and even outlook of life. Though she may not be great in her studies, she is a happy-go-lucky girl who always manages to pick herself up after being tripped by obstacles. Lost her mother at a young age and thus has a close and strong relationship with her father.
She sees Naoki as her greatest dream and he is the main source of motivation in whatever she does. Her strong determination and desire to succeed can be seen in her striving to be top 100 in the mid-term examinations, the preparation for the cross-country race...etc. However, she tends to be over-exaggerated in her actions and occasionally, her 'big-mouth' and enormous laughter can really 'traumatize' Naoki. By the way, Kotoko is also a horrible cook and this is bewildering to Naoki as her father is such a great sushi chef.
But when Kotoko gets serious, she
really means business. For example, this can be seen in the way she chides Naoki for not
respecting his elders and not showing enough care and concern for his younger brother.
Overall, she is quite innocent and cute, be it in her thinking or behaviour. Sometimes,
her simplicity is also quite overwhelming and in my opinion, it really shows through the
way she collects all kinds of amulets for Naoki. (See picture on right >>>)
One thing to note is that Kotoko is definitely not being stupid in her pursue of love. It may seem as if all her integrity and character is thrown out of the window amidst the course but if it's her decision and dream, we cannot really fault her for it. She just feels happy doing things for Naoki, no matter how unappreciative the latter may be.
She does display her mature thinking at various parts in the show, especially those portraying her with her father. It is particular evident after her two years away. We can see a character development from there, tending towards being more mature and sensible.