Someone has find a solution on the french part of the forum.
I write it here :
On PC, on your browser, use the link : https://www.hentaiclicker.com/?tc1=HHae7050ef6tf2add1c0b83f0e0e78d4c1&tc2=14540&tc3=174&noagev=1&ref_type=crosspromotion&ref_id=XXXXXX&game_id=25&auth_id=41575
but use your ingame ID of HH instead of "XXXXXX" (you can find your ID in your ingame profil, where you choose avatar)
-> Then, load the HentaiClicker page with the link with your ID (the entire link, not just the part that can be clicked here in forum)
do your connexion on HentaiClicker, do the things to have Mizuki (lvl3000)
-> Reload your HentaiHeroes page to have a new banner to collect Mizuki, just accept and she is yours
(note that you probably need to avoid adblocker and so...)
Hope it will work for you