Ending shows 4 options: MC turns females, ends up with Ritsuka or ends up with Shiori. Then MC turns male, ends up with Ritsu(female) or ends up with Shiori (male). All are different timelines/or AUs.
Putting it into the read BL list 6 as I shipped Shiori X Male MC
Seibetsu "Mona Lisa" no Kimi e.