You still need to collect the King of the Sea. Try to construct the sanctuary, upgrade your luck in it and then fish.
If you got the 3 artifacts (King of the Sea, Crown and Fruit) and the game did not finish, please send me a message latter and I’ll try to fix it.
The seed occupies the same space in the inventory as a limitation of how I implemented the game. But after getting the fruit, you were not supposed to get it again :p.