Shugo Ohkawa is the son of Meiichiro Ohkawa and had same as the incident as Naoya two years prior.

"According to Mitsuru's [testimony], 2 years ago, in 1924, [something] happened in 12-Story Prison. A senior colleague of Naoya and Mitsuru whose name was Shugo Ohkawa hanged himself and died. The incident [was] judged as a suicide and went [under] gag law." -Ingame Evidence