Akai Yubi

A shocking incident is the start of a tragic chain of events that befall an ordinary family of four: Maehara Akio, his wife Yaeko, their son and Akio’s elderly mother, Masae. Akio is a commonplace company employee but has to carry his family’s tragedy on his shoulders as a psychological battle unfolds between himself and Kaga Kyoichiro. In order to get the Maeharas back to being a genuine family, Kaga disentangles the complex web of family interactions with his keen perception. Just when it is determined that the case has been solved.
(Source: Jdrama Weblog)
~~ Adapted from the 2006 novel "Akai Yubi" (Kaga Kyoichiro Series #7) by Higashino Keigo.