I have basically gotten up to the point where I have the sewers with Asara as the only other active quest but Mizuki is still "go to the guard's office during daytime".
Might be a hint bug. Proceed with Asara. Also, what's the last Mizuki event u've done?
The Karaoke event.
I did merge Mizu events with Willow's. Maybe sth broke for u. Did u update to 0.27 mid game?
What events did u do with Willow?
I did update, it might have broke something. I have done the Willow goes to the guard's office and that's where it stopped.
U should be able to fix it with the console. Check the m.story variable. Should be equal to 5. If it's not, then use m.story = 5
If that still doesn't help, try w.story = 2
Try entering both at home and then go to the office. Google renpy console if u don't know how to use it.