VN Ren'Py Eternum [v0.8.6 Public] [Caribdis]

[Bromo]

not 100% sure about that
as far as I know:
the Harem route is the "real/true" or cannon ending
but maybe solo path will be added later but are not in yet

 

[Finuee]

is there a solo romance route in the game or is the story built purely around a harem?

It's basically a harem game, trying to play a solo romance route will leave most of the content out for you.

 

[Takkatakka]

It's basically a harem game, trying to play a solo romance route will leave most of the content out for you.

Yeah, you technically can do solo routes, but it really isn't build for it and apparently can also lead to some weird bugs and inconsistencies.