This is a beautiful story of straightforward naughty Girl "Belle" and studious boy "S", who don't know what is Love
Belle fall for him even he is 3 years younger than her, at first, he is minding his own business, when she graduates and leaves him, he starts to feel her Love.
Its cute love and it shows the feeling of S being a small boy, and how he handles his emotions. Meanwhile, as you can the title itself secret love, One of belle's friend is has a secret crush on S, and she sends him cards written in another language. When S finds it, he starts feeling his own hidden feelings.