Ralph event

I think you're talking about the dialogue after the end of Dora the Endorser Pt. 5.

You get some dialog between Clancy and Ralph Wiggum. Afterwards you'll see a system message.

System Message: Take a look at what’s on the menu for Ralph at the Happy Sumo. Complete Akira’s quests to find out!

In other words, this questline will open once you've purchased The Happy Sumo.