Honestly, it became a mess so fast.
Also, before Haruka interrupted sensei had her lips completely ready for her 2nd high schooler kiss. Was kind of annoying how she was so easily swayed by Mizu. I mean, is not like sensei has anything actually going on with Haruka but still, even without any blackmail she doesnt seem to care about her position as teacher.
This whole Mizu plot just felt like a big shallow improvisation.