Both are mystery drama, centering an incident from past. There are also loose similarities between them - most notably on the rate of story progression, character settings and glimpses into the lives (current vs past situations) of main characters. Reverse focuses more on the characters' involvement in the past incident while Gekiryu is more about present time.
While watching "Gekiryu~Watashi wo Oboete Imasuka?", I felt the same bittersweet feeling with "Piece". The plot is similar: former friends from high school try to resolve an accident which occurred many years ago. Step by step, layers are shown, prejudices and lies are revealed. During this journey, they will question themselves about the meaning of their present lives and learn about each other. "Piece" has more mystery, "Gekiryu~Watashi wo Oboete Imasuka?" is more focused on the people’s lives.
