^Yeah, they care enough about each other to do anything and everything for each other, but aside from some fond back stories they have, the only remotely romantic sounding thing that's not too subtexty is Marcille declaring her reason to follow Laios to save Falin while they are all penniless by saying "Watashi mou Falin no koto dai suki da mono!" (translate how you will) in ch01/ep01. That's already more canon fuel than lots of other ships :))