Because of storyline reasons, Kiwami 1 felt really depressing and sad, since a lot of shit happens to Kiryu, especially with him coming out of prison and the whole thing with Nishiki. Compared to 0, Kiryu felt like a broken man. It was nice to have Majima there for him, training him up again. A real bro.
Edit: Also with Japans bubble economy from the 80's which had burst, the world felt like a good reflection of the times. It felt so much different from the 80's. Kamurucho felt like it went through a huge transition.
