How do you think the story will end (despite not knowing how many volumes are planned for the series)? For me, there are three main possible endings:
1) Shin went back to his world alone
2) Shin went back to his world with the females who have romantic interests in him
3) Shin decided to stay in the current New Gate world with the females who have romantic interests/feelings in him
Also, who else do you think is romantically interested in Shin except for obviously Schnee and Tiera (and maybe Yuzuha should it recover its memories/mature mentally enough)?
What are the chances that the First Princess (not appeared before Shin yet) or/and the Second Princess (Rionne Strail Bayreuth) to eventually develop feelings for Shin after travelling with him? (It is possible for the Second Princess due to the current events in volume 4)