Honestly the romance is kind of confusing but the emotions are so pure I don't even mind.
Unless you can confirm that from the webnovel with no GL tags, we shouldn't. Yet. The dialogue and art I saw for the novel are about 50:50
very blatant GL
(mouse Elodie proposing to Sera?) to Het
(ML kneeling to probably Sera but Elodie in the middle sharing the veil? what??). The writing is affectionate. GL would work. I don't expect it'll be treated as the same kind of connection as het romance, but the besties are clearly the main relationship.
But the age gap throws romance off. Sera (15-17ish?) sees Elodie as a 5 year old little sister early on, while Elodie has known her for 15ish years including over ten after Sera's marriage. So Elodie thinks of herself as similar-age friends and falls into problems of child genius protagonists. Hopefully the time travel isn't kept secret but that's very awkward mismatched bodies and expectations.
Still the girls are so affectionate that at worst this story will be basically homoromantic (possible polyamory on the side). That's not bad at all. At the same time I hope the author actually tries to navigate the awkward problematic GL they're absolutely teasing. As of now the ending isn't written.