Ok, here is the walkthrough to each of the endings:
Good Ending
1st method: You win all of the trial without cheating on her. (I tested it but i don't know if it the same to other, but it doesn't matter if you nail or mess the dance up. it will still give you the good ending)
2nd method: It fine if you lose some trial as long you win most of it, You don't cheat on her and it led to a good ending
(3 sex scene)
Gangbang ending
You win all of the trial, but you cheated on her with Olunchi and Amara. Doesn't matter if you nail or mess the dance up, it will still lead to the gangbang ending where John will die (9 sex scenes, including the gangbang)
John have two option at the dance, the fully grown butterfly (Olunchi sex scene) or the unhatched cocoon (Amara sex scene)
Tribal life ending
You lose all of the trial (Which Claire become an slut on day 5), and on day 6, Chief pinu gave you three question of which animal you would fend off, the wolf, the crow, or the boar. (They are all the same since it lead up to Claire being drunk and mistaking one of the tribesman as his husband, John and she get impregnated), John became an cuck, allowing Claire (The goddess of Ikapati and Claire are fusing together) to do what she want and she wanted to live on the tribe which John agreed.
(11 sex scene)
And i think that is all of the ending and ways to reach it i found. if you reached all 3 of these ending, the gallery will be completed, and all of the clothes and accessories will appears. allowing you chance what they look like (Only standing model, doesn't affect the sex scene or interaction) and that is all.
Plus: I believe NTRMAN next game will set in space as we saw after we got the ending. Each of this game is set in the same universe (Tenant of the dead -> Arrival of the goddess -> (Space game which NTRMAN gave hint after the endings)