Castlevania: Harmony of Dissonance
Many years after Dracula's last defeat at the hands of the Belmonts, Juste Belmont, grandson of Simon (and current owner of the Vampire Killer, famed whip of the clan) encountered an old friend, Maxim Kischine. Maxim had left two years earlier to go on a training mission (Maxim was a vampire hunter as well, and was just a little bitter that his friend got the Vampire Killer as Maxim felt he was the better warrior). Maxim returned suddenly, suffering from amnesia about the last two years, but with the knowledge that their friend, Lydie Erlanger, had been kidnapped. The two hunters headed out to the location Maxim was able to remember, a mysterious castle that had just suddenly appeared.
While Maxim waited at the gates, healing, Juste went inside to find his friend. What he found inside, though, was much more than he could have expected.
As he learned inside, Juste was in Dracula's castle, the creature of chaos that heralded the demon King's return. As Juste explored, though, he learned that Dracula had not returned. Instead, someone else had brought the castle back... that someone being Maxim. Maxim had gone on his training mission wanting to redo what Simon had done so many years before: unite Dracula's body parts and destroy the beast once and for all (except, of course, Simon hadn't managed to make it stick even then). The fame Maxim felt he would get from that feat would overshadow Juste's accomplishments.
Sadly, Maxim was not strong enough to ward off Dracula's presence and, instead, became the host for the Dark Lord -- which had the effect of splitting Maxim's personality in two, a dark and a light side.
Juste battled his way through two versions of the castle (one to reflect each side of Maxim's mind), until he finally came face to face with the Dark Maxim in a final confrontation. Battling Maxim, Juste would have killed his friend if he had to, but Maxim snapped out of it and shook off the presence of Dracula. The Dark Lord, in a wraith-like form, then attempted to destroy Juste, hoping that the blood of his sworn enemies would fully resurrect him. Juste, however, was able to defeat the wraith, banishing it back to the grave. The castle crumbled around them as the three friends escaped, lacking Dracula's presence to keep it whole.
Juste is Simon's grandson and natural heir to the whip. Why Maxim felt he had any claim to the whip is not made clear. One could assume he just felt he was the better warrior and had a claim to it for that reason. As the previous game in the series (Circle of the Moon, released in 2001) proved, greedily desiring the Vampire Killer only makes it more likely you won't get it, and more likely you'll be taken over by Dracula's dark powers.
Part of Juste's power comes from the Belnades clan. The implication is that he inherited this power from Sypha Belnades, wife of Trevor Belmont.
Juste wanders the castle collecting, among other things, Dracula's body parts. This is similar to Simon's collecting of the body parts in Castlevania II (as well as in Symphony of the Night, which was also referencing Castlevania II).