This 12-episode series debuted during the Summer 2018 season but is based on a shonen manga which concluded a decade earlier. Because it started weeks later than normal, it never got Preview Guide coverage that season or picked for streaming reviews. Despite that, it proved successful enough that a second season is airing in the Summer 2020 season and Funimation is not only picking up the title but also planning to dub both it and the first season. (Crunchyroll still streams this first season in subtitled form.) Before the second season starts, let's look at what made the first season a success.

At heart, the series' concept is a standard “protagonist has a job which involves putting down dangerous supernatural critters” set-up, down even to the protagonist having a former friend who has turned evil. The one minor difference is that Muhyo is a bit of a bastard himself. He is arrogant, can be quite ruthless when dealing with spirits, and has a signature sneering chuckle which he uses in just about any situation where his equally-signature annoyed “tch” does not apply. He does not totally lack compassion, and does trust and support Roji, whom he personally chose as his assistant for reasons that the series has not yet clearly delineated as of the end of the first season. Despite this, he comes off as a likable character, and has the much more compassionate and sociable Roji (who is effectively the series' conscience) to balance him out and look after Muhyo.

The cases the duo handle (often with at least one person tagging along) tend to be about one part mystery, one part action, and three parts horror, with occasional minor doses of humor mixed in when evil is not being confronted. Though styled to be accessible to younger audiences, the horror elements are definitely not kiddie fare; the more extreme cases, such as the spirit girl who rips people's faces off, stand at the absolute upper limit of content appropriate for early teens. Many of the methods of exorcism that Muhyo uses have horror themes to them as well, such as the fleshy box with teeth around its lid (Beelzebub's Treasure Chest), and except for the cases where individuals are sent to the River Styx, they invariably have a hellish and/or diabolical theme to them. One or two references are made to Heaven, but what little has been shown of the cosmology so far suggests a mishmash of supernatural elements from multiple religions.

Episodes 1-3 and 6 are basic “monster of the week” formats, with some of the episodes split between two cases. Episodes 4 and 5 compose a mini-arc about a visit to a Magical Law home village for Roji's advancement testing, which brings overall villain Enchu into the picture. That provides some of the set-up for the Magic Prison arc, which composes the entire second half of the series. Each story adds new characters into the mix, some one-shot and some recurring. Of the latter, the most prominent one in the first half is Nana, who keeps popping up even after her case is resolved in episode 2; she does not amount to much more than being the token female character, the token “normal” person, and sexual harassment bait all rolled into one, however. Important characters for the second half include the artificer Biko, Biko's sensei Rio, and to a lesser extent Muhyo's childhood friend Yoichi and fellow executor Reiko.

The visuals for the series most stand out in the dramatic Magical Law invocations, which are elaborate and visually creative affairs often featuring each episode's most extensive animation sequence; a video summarizing these would probably make for better advertising than a trailer featuring the characters. Character designs for Muhyo and Ryoji are tailored to exploit a recurring joke about them resembling an onion and bean sprouts, respectively, while designs for female characters tend to swing between extremes: they are either very feminine or very not feminine, to the point that two of them could easily pass for boys. (And given that one of them speaks in the kind of husky voice that would typically be associated with a female seiyuu voicing a teen boy, that impression is probably intentional.) Spirits typically get decent-quality CG animation, but outside of exorcism scenes, non-CG animation quality is more limited. Except for one or two scenes, the visuals more imply graphic content than show it, but the series still has some visual content that would be edgy for younger audiences.

The musical score consistently hits creepy and dramatic notes for its featured scenes, though the styling is more typical of younger-skewing horror than more adult-oriented horror. It also effectively mixes in some piano pieces in an episode featuring a piano prodigy. Opener “Gifted” is a solid rock number, while closer “Hotohashiru” is a lighter and more playful number.

If Muhyo & Roji's Bureau of Supernatural Investigation has a message to it, it's “treat people like crap and they can come back to haunt you – literally” and, to a lesser extent, “jealousy is one of the roots of evil.” The origins of nearly all of the spirit cases and cases of characters turning to the Dark Side come down to one of these two points. The writing never moralizes this, instead allowing viewers to come to their own conclusions. That and the later development of a more substantial plot help make the series better than it initially might look like. Combine that with the flashy, creative exorcisms and it's no wonder that the series proved popular enough to actually get the continuation promised at the end of the last episode.