What is Sengoku
Made in 2011 by Paradox, the same company that makes the huge Crusader Kings 2 franchise, Sengoku was sort of(not entirely researched) built on a pre-engine that was eventually used to make CK:2.
How's it compare to CK:2
I've read many forums to cultivate this idea: It generally is taken as a Grand Strategy-lite game that doesn't have the robust features and long-lasting gameplay that CK:2 has, but definitely shares notes of focusing on individuals and their politics somewhat more than war-features.
Just like CK:2, Sengoku has its many historical errors, but as a videogame, it's one of the only games of its kind and thus also has more historical accuracy for it.
There's a niche Paradox fan-base that absolutely loves the game, but says it's likely been permanently abandoned, but it's still quite playable and enjoyable.
The Warring States. This is Feudal Japan - a harsh time, but subsequently a very interesting time historically. Many Warlords have split Japan into over 350 different territories and are all, basically, battling it out for control of Japan.
There's really only one mod I could find so far - I'm having a bit of trouble accessing the Paradox mod sub-forum for Sengoku, even though I registered my copy, but the one mod I did find is praised for being pretty amazing, but unfinished.
The modder jumped ship to work on a giant mod that basically puts Sengoku into Crusader Kings 2, but people are enjoying the modders Sengoku mod and find it still adds a lot to the game.