I can not get either of Gunthers scenes to unlock and Ive tried everything. His bond 2 event just keeps repeating over and over and "that offer..." choice in the backyard is always unaccessible.

Yeah me too. It't kind of annoying. I think the new update which just release might fixed it I guess ?:?

first, you need 20+bond point, and you should have already had a drink with him. then when it gets to your free day, go to your room and masturbate, there is a chance that Gunther will show up and 'help you out'.

Oh nice~ Thank u.

i got the  "that offer..." button once but when I went to the place it doesn' appear again even if I start a new game. Is this a bug or am I doing something wrong?

It only appears once. If you want to get the other scene, you're gonna have to load the time before you got the choice and pick one of the options you didn't initially pick (the one that required 8 str and the normal one). If you need to unlock the one that has 8 str but haven't gotten 8 str by then, you'll have to move back and cancel the interaction until you get the strength to unlock that scene. If it's the normal one, you just have to load it back and pick that option instead.