A supernatural romantic comedy, Renai Kaidan Sayoko-san will leave you laughing one moment, laughing another moment, and laughing even more. The greatest strength of this manga is its well-written comedic moments. The story does not feel forced and flows well, although as a slice of life manga, there are not too many notable developments. This is not an issue, as the development focuses primarily on the characters and not the story or world.
Starting first with the characters, we have your generic but believable protagonist, Inaba Den. One thing I like about seinen romances is that no character is perfect, and acts in ways that are similar to a friend you may know in real life. Inaba definitely has many traits which I see in my friends all the time: reusing plastic bottles to put your own tea in? Check. Being incredible dense to his own romance, but relatively sharp regarding others? Check. Not believing in the occult but being too nice to say otherwise to someone who does? Check. Meanwhile, we are introduced to Sayoko in a slightly negative light - she's a strange character. And while she retains her quirkiness throughout the manga, we see - once again - many of these real human traits within her. As we continue reading, it is difficult to not relate to Sayoko's troubles in pursuing Inaba, and we feel a strong desire to support her efforts. For sure, stalking your crush is definitely on the creepy side, but I think many of us have also happened to "coincidentally" run into their crush before. Or perhaps you've also felt flustered and avoided your crush after confessing to them. Although it may be difficult to relate to these characters on a personal level, there are many personality traits and events which make you think, "Haha! I had that happen to me before, I know how exactly that feels." Unfortunately, with these types of characters, that also means that few of them particularly stand out. Although I do like the characters in this manga, if you asked me to pick a favorite, I would not be able to choose any of them.
Moving onto the artwork, as another user has mentioned, Renai Kaidan Sayoko-san has a more shoujo-y feel to its art. It is not dark and sketch-y like many other seinen manga, but I do not feel that is particularly an issue. One thing I particularly like about the artwork is how the author uses different sections of a pattern for different sections of Sayoko's kimonos - instead of using one large pattern for the entire kimono (looking at you Boku Girl). The characters are all distinguishable from each other, although some of the female characters share similar faces. Even the less-frequently-seen side characters are easy to identify. The only exception to this are the many spirits which accompany Sayoko: although they vary greatly in their designs, many of them appear only once or twice and are quickly overshadowed by the main spirit-cast. Aside from this, my main complaint with the artwork is that frequently, the author draws the human characters' hands as being far too thin and/or elongated. Sometimes the anatomy exaggeration is played for comedic effect, but it can be quite distracting in more serious scenes.
Overall, a summary:
+ Great comedic moments.
+ Realistic and varying cast of characters.
+ Easy to get into, little investment needed.
- Mediocre story, slow paced.
- Does not leave much of an impact.