First and foremost, I'd like to mention that I've read the manga before watching the anime, so half of my review will most likely be based on how I percieve the anime in comparison to its manga counterpart.
Uramichi Oniisan has a certain appeal that could seem dark to some - it plays with common tropes people experience in their daily lives, yet exaggerates them for comedic effect. Personally, I love the dark humour, sarcasm and all the ranchy jokes this series has to offer. I know for a few people it may be too exaggerated to the point of being simply annoying, or just "trying to hard to be funny", but, I'd beg to argue that Uramichi Oniisan does a very good job of meeting the balance between seriousness and humour.
The different characters in the show are quite diverse and all seem to interact with the titular character in various ways. I'd also like to mention and emphasize that I believe the voice actors chosen for this series was very well done as these actors certainly understood the assignment and knew how to portray their roles.
For instance, Hiroshi Kamiya (most famously known for being Levi in AOT), plays Uramichi and honestly I wouldn't have it any other way. He's able to capture the depressed tones of Uramichi perfectly, yet also emphasize Uramichi's sincerity when it comes to certain characters. And I cannot stress this enough, but the character Uramichi is probably one of the most well-written characters I've seen in anime (although some may beg to differ). I love how he realistically presents negative views on the life of a working adult and how it's not all sunshine and rainbows - his minor fourth wall breaks are excellent and definitely keep the viewer captivated.
Other than Uramichi, I'd also like to touch upon my personal favourite character - Daga Iketeru. I will admit that I first only liked him because he was a pretty boy, but once seeing his character unveil in the story, it was quite interesting to see how he's portrayed to be a child living in an adult's body. He's quite unaware of himself and his abilities but at the same time I like the mystery surrounding his character. Also I'd like to mention how Miyano was the perfect person to play this character, namely because of how authentic he comes across. I'm definitely looking to see more of his character in future episodes.
Music and sound in general plays actually quite a big part in the show. I never really expected how it would impact my enjoyment as a manga reader, but once getting around to watching the anime, it is definitely clear that the creators knew what they were doing.
If we were to go by the ending song and opening song only, I'd say that they're both perfect fits for this show. The ending song sung by Miyano, has become quite a hit as of current and I also really enjoy it. I like how it contains calmer and more 'adult' vibes, as if representing the end of a long day at work and overall nostalgia. I think Mamoru Miyano definitely did so well on this track, and I'm pretty certain a lot of fans enjoy it because of its 'kpop sounding feel'. The opening song is quite upbeat and what I'd imagine the theme song of Together with Mama to be, I liked the images portrayed in it as it made it quite cute and overall just portrays the anime to be your general slice-of-life comedy type show. The background music and it's overall build up and slight changes in tone honestly just adds to the comedic effect as well as setting the scene, making it a necessity that not one would think of at first glance.
My review may be a bit biased, but I just want to put it out there that Uramichi Oniisan as an anime was done quite well! The overall flow of the anime is reminiscent to how the manga flows with it's short cut offs, but I believe it just adds to the charm of the show. And honestly, the show is literally just comedic genius with just the right amount of fourth wall breaks and seriousness to keep that mysterious allure about it. So if you're hesitating to watch this show, I hope I've convinced you to forget about your worries and just watch it!
