Eien no Ko (J-Drama) (2000)

When three 12-year-old victims of child abuse are introduced to each other at a mental hospital, they form a bond that proves to be unbroken by personal growth and adulthood. After saving Yuki, from drowning in the ocean, Ryohei and Shoichiro consider themselves her protector….a feeling that carries over into adulthood. When the three are reunited seventeen years after meeting at the mental hospital, they find that their feelings for each other are just as strong as before. Yuki now cares for others as a nurse, Shoichiro is a controlling lawyer, and Ryohei is a career police investigator. When a body surfaces in the local river, the three are drawn into a series of murders to which they all feel powerfully connected… -NTV
 
This drama might not be suitable for some viewers because of the occasional violence.