The Art of Loving (2001)

Blurb:
As the son of a prominent and wealthy family, Yutaka wears the mask of a genteel elite student. Frustrated by this facade he must put up with and stifled by a future already laid out for him, the only way Yutaka can deal with the boredom and unhappiness of his empty life is through sexual release. Then one day, Tohno - a delinquent-looking student with blonde-dyed hair - suddenly transfers into Yutaka’s class. As he finds himself more and more obsessed with a deep abiding lust for this young man, his daily descents into sexual fantasy begin to interfere with his life, until a ferocious impulse to possess Tohno for his own leads him to a diabolical scheme.

Source: www.anisearch.com/manga/2553