If you find yourself going insane from trying to get the old codger Heikichi to give you information in Chapter 6 of Missing Heir, know that you are not alone. He certainly seems to have a nice tidbit of information regarding Yukiko, but chooses to be annoyingly coy about it, even after you’ve seemingly used every option at your disposal. Thankfully, you can preserve your sanity by doing the following things to get the geezer to cough up what he knows.
Once the hard-to-swallow dialogue is out of the way, Heikichi will finally let you know some valuable information about Yukiko, and you will be able to get on with your investigation.