In 16th century Japan the African slave of a Jesuit priest rises to become a samurai in the service of its most powerful warlord and faces a corrupt general who plans to topple him.
The characters and the setting are interesting but it seems to me that you focused too much on this and not enoght on the plot.
I suggest to introduce a personal goal for the hero and to introduce a clear inciting event (what puts the story in motion).
I think the sizzle in the script– the feature of the script that grabs attention, wets interest –is the situation. Based on real events, a Black man become a Samurai in feudal Japan– wow! That’s different, that’s unique.
In this case, I think the plot is secondary in terms of getting the script read. But important when it come to getting the script filmed.
Maybe something like:
Based on actual events, in 16th century Japan, an African slave rises to become a samurai serving a powerful warlord where he must survive plots by jealous rivals to kill him. (31 words)
“Based on actual events” — because it’s so incredible that without it, it might be dismissed as fanciful fiction. The logline needs to convey the message “Truth is stranger than fiction. This really happened, folks.”
“A powerful warlord” rather than “its most powerful” –Could go either way, was just looking for the minimum number of words to make the maximum impression. Good enough to get the point across.
“Jealous”. Surely it was not just a matter of the general being corrupt. Would it not be the case that his motivations were overdetermined and included jealousy? And , would there not be others who felt the same way? He may have been the primary nemesis, but he can’t have been the only one who was offended by the very notion of an outsider, a Black outsider, being accept into the ranks as a samurai.