Note: I rate stuff relatively, with a 50 being average. 73's a good score.
This review is spoiler free.

Lady & Oldman is the story of the titular duo, who work as couriers in a 1960s American Southwest. "Lady" is the daughter of a former mafia man, and "Oldman" is an immortal who's just finished serving out a 100 year sentence for a crime he didn't commit. Throughout the series, the pair navigate through a complicated web of interactions between the mafia, a conspiracy of immortals, politics, and their own family ties.

Overall, the series feels to me like a much more polished version of ACCA 13. The conspiracies are unspooled more deliberately compared to ACCA, and the world... man. There's a bunch of little locations, and they feel lived in. There'll be a diner, or someone's meeting spot, and L&O does an amazing job of making it feel like you're there, just hanging out in whatever slice of Los Angeles.

In keeping with a really realistic feeling world and Natsume Ono's style, the characters are the focus and they are excellent. Lady & Oldman isn't particularly a slice of life series, but you get enough glimpses into the everyday lives of the characters to make them feel like people. A couple pages of characters talking about what foods they like, or listening to music, or just discussing something fairly mundane appear in every couple chapters, and that helps a lot in understanding the characters better. Their motivations are clear, their personalities are strong, and when there's a major character moment it feels incredible. It's a great feeling of wanting to root for the main cast to succeed, and just makes it really fun to follow them around.

The overall story is solid. I can't say too much without getting into spoiler territory, but "Oldman" really wants to find one person, and for various reasons political and mafia factions are also looking into that person and Oldman. The series shows a lot of different points of view, especially towards the middle of the series, and when they all collide towards the end it makes sense. Motivations are consistent throughout the entire series, but you get more context as to why characters have them over time. I don't know how to put it, but everything just makes total sense when it happens, the characters' emotions are perfectly done, and it's just very satisfying.
The political and mafia elements are pretty light- at the end of the day, this is very much the story of Lady & Oldman, not Lady & Oldman & some yahoos. They're done decently, but if you're looking for a crime-focused story, this probably isn't for you. The overall appeal of Lady & Oldman is a lot more in how the characters behave and interact, not necessarily the situations they get caught up in.
In the same vein, the series doesn't fully explore how it does immortality or anything, but you get enough for the characters at hand.
The ending is wonderful. It doesn't tie a neat bow on the characters' lives, but that's fine! Almost preferred, even. The story being told is wrapped up nicely, and ends exactly where it needs to.

The art is fine. Weird style, a few pages look really nice, but overall it's just clean art. I really like how the character expressions are drawn, but otherwise it's good but nothing crazy.

Overall, if you're looking for a satisfying character-driven story, this is for you. It's a satisfying time, the character work is great, and the setting is immersive. Just a wonderful character-driven story that's well worth the read.