In the Pretty Babies series: 5j1d

Part 1 - Pretty Babies (1 Volume - Complete)
Rookie detective Chikara has been assigned to the close minded, hard-faced senior detective Ibuki, One day, Chikara, who had tailed Ibuki in order to uncover his secrets, witnesses Ibuki carrying a suspicious heavy bundle out from a church. Then, after almost being run down by a car, Chikara is asked to spend the night with the beauty who'd been driving in lieu of compensation...?!

Part 2 - Heavy x Beauty (3 Volumes - Ongoing)
In the middle of the night, Ibuki suddenly calls on his superior Kiriya. Both work at the Metropolitan Police Department and have been dating each other for the last three years. One day, Kiriya's uncle proposes to headhunt Ibuki, and talks of Kiriya's own arranged marriage introduction.

"Hmm, I guess it's high time." Kiriya sighs upon receiving a phone call from former bad company...