Sure. The Ouran Host Club manga has finished. It had a proper conclusion that covered all the important aspects and left a lasting impression on readers.
Romance is also a big theme. The OC usually gets involved in a romantic relationship with one or more of the host club members. It could be a slow - burn romance or a love - at - first - sight kind of situation.
One common theme is the discovery of new sides of the characters. When a baby is introduced into the story, the hosts who are usually all about entertaining guests in a sophisticated way, now have to show their nurturing and caring sides. Another theme is family - like relationships. The hosts come together to take care of the baby, which is like a little family unit within the club.
The Ouran High School Host Club manga is indeed complete. It wrapped up with all the storylines resolved and characters' arcs concluded. Fans got a satisfying finish.