Both drama are detective-based. But in 99.9 Keiji, the protagonist is a lawyer(yet, most of the job he does is detective-work). Like Ibuki in MIU 404, Miyama in 99.9 Keiji is a funny guy. Moreover Miyama's partner is even dumber and funnier in contrast to Ibuki's partner who is not always funny. If you like the humour part of MIU 404 then 99.9 Keiji must be your next stop, as it delivers humour at an even higher level.