This was the first drama I ever watched back in 2005. So you could say it was the series that brought me into the world. Its a very well-known story, adapted from a book as they commonly are and has different versions in many countries. Japanese version stars Nishikido Ryo (Ryusei no Kizuna) I highly recommend this for any avid watcher who has not seen it or anyone thinking of starting their first series.
Warning: the title is self-explanatory, its tear jerking one.
Drama Wiki for full synopsis. I say you just watch it without any premise and let the story unfold. I will say that the genre falls under the following: life, school, romance, family, human… disease. (Spoiler? lol)
aparoo says 5 litres of tears / 5 litres of tears