Renai Tsuu summary:

When stoic Mizusawa, a janitor, saves businessman Aoki from falling down some stairs, he gets a friend for life! Aoki is always tracking him down at lunch time just so they can eat together. But Mizusawa isn't sure how he feels about Aoki...This is a series of six. The order is:1. Hada na Ue no Renai Jijou2. Zaiaku wa Hada no Ue ni (same characters & issue but different plot)3. Zaiaku wa Hada no Ue ni-Hada no Ue ni Furu Hana*4. Renai Tsuu5. Renaitsuu-Akka-*6. Pillow Talk + Holiday*(*) indicate djs.4 and 5 are spin-offs featuring Aoki and are contain events from Zaiaku from Aoki's perspective.6 features both couples.