https://store.steampowered.com/app/2992110/DLC__The_Last_Tower__DLC_Pack_of_Minimalist_Tower_Defense/
Thank you all for your long-term support! The development of Minimalist Tower Defense DLC "The Last Tower" is nearing completion and will be released on June 14th
(Anyway, it's about to be released! Hmm! There are only so many announcements left!)
Oh! You found me! In fact, after owning the Supporter Pack, if you pass 5-S, you can permanently obtain the Towers in DLC by input "happy"