Finally figured out how to get Mizuki! If you played Hentai Clicker and did not get her, don't use same log-in / password again. Won't work. Instead follow these steps:
(1) On Hentai Heroes, go to Sex Friends (tap the blue icon with 3 horizontal bars on top right of screen)
(2) The "Crosspromo" banner for Mizuki is available here. Tap "try it now" and it will take you to Hentai Clicker.
(3) DO NOT LOG-IN on Hentai Clicker. Instead start a new game from Level 1.
(4) After a few level ups it will ask you to register.
- If its your first time playing Hentai Clicker, then you can use same log-ins as in Hentai Heroes.
- If you have previously registered on Hentai Clicker, DO NOT USE SAME EMAIL LOG-IN / PASSWORD. Use a different email / password to register, and carry on playing.
(5) When you level up enough to get the "Forge" option, choose it. You restart from level one, but level up faster. Once you reach Lv 3000, a pop-up message appears telling you that you obtained Mizuki on Hentai Heroes. Refresh your Hentai Heroes page and voila!
On Hentai Clicker, I chose to purchase 45,000 Kobans for USD 5 so I could buy stuff from shop to speed up clicks and level up faster. Even after reforging once, I managed to get to Lv 3000 in 1 hour (without having to click like crazy). So I recommend this purchase, otherwise it will take you the whole night to get to Lv. 3000 and with severe finger cramps