My Huckleberry Friends (Cdrama) <--- This one fits perfectly your needs. At first it's even annoyng how ML is attached to FL, but I found this show very touching. Every character is important, and the romance is sweet despite it's slow.
The Eternal Love 2 (watch season 1 first - the ML quickly comes to prioritize her in that season too - e.g. he gives up his best chance at becoming crown prince when he learns that she might be in danger - but in season 2 the circumstances are a bit different and his world really revolves around the FL)
Bloody Romance (warning: it has a disturbing and tragic ending)