After Julian and the other Shinon settlers escort Monica back to Roanne, Julian will be given an offer to become a guard for Monica. He accepts in all the other character's routes. You can turn down this offer if you so choose to. On the first day he is to guard Monica she gets captured and Julian follows the monster to a cave where she is found unharmed. Inside, they find Godwin in hiding, but he escapes capture by causing a cave in. Michael overlooks Julian's blunder since he found Monica and was able to force Godwin out of hiding.
The Next day he is given a task to escort Monica to Zweig to be married. Monica doesn't want that and she wants to leave the castle, You can either accept Michael's request to escort her or flee the castle with Monica. If you choose to escort her to Zweig, the ship she is on also holds goods that cause monsters to attack the ship. Julian and Monica escape to the deck, defeat the monsters in their way and abandon ship, however this causes her to be seperated from Julian. If you chose to follow Monica's request, then you both leave the castle and go out into the world.
If you chose to leave the castle before Michael orders you to take Monica to Zweig to marry her off, and you have her in the final party, Michael will congratulate you as being a successful guard to Monica and Julian will be given the title of Baron at Monica's request.
Julian (played by Murase Fuminori) in Romancing SaGa the Stage: The Day Roanne Burned
Gian from Romancing Saga: Minstrel Song actually does resemble Julian. His hair is silver color, his shirt is teal and his attitude is far more clumsy than Julian's. However considering the fact that Monica from the PS2 remake looks exactly like Monica from Romancing Saga 3 rather than in the original, this is unlikely a coincidence. Gian and Monica are a couple, whereas Julian and Monica are definitely not that much different. Also, it is not confirmed if Gian in the original Romancing Saga was that game's Monica's boyfriend or if this was all added to the PS2 remake.