Darker than Black: Kuro no Keiyakusha - Sakura no Hana no Mankai no Shita

Diving straight into the review.

Story: If I was to rate this OVA just from its own story, I would give it 2 because of its simplicity. But don't forget that you need at least 14 episode of background information from the normal DTB (best viewed after some time has passed after you finish DTB, good for some quick laughs.) This OVA is more of a side story to the original Darker than BLACK. A contractor was killed and supposedly his corpse or his belongings are hidden under the sakura tree. Centering around Mayu Otsuka, this provides a good deal of laugh and makes you remember ... those good ol' times with DTB.
8/10

Art: Excellent art, neatly done and no details were missed. Everyone is well drawn and the background always mean something, they don't just stand there. On a side note, I really like how they draw the eyes (especially Yin's.) The same quality as the original DTB, maybe even better. Although I found it strange that there was no blood in the perverted contractor scene, it's not like some other anime that the blood is black and disappears in the very next scene.
10/10

Sound: I always liked the opening, and the fact that they didn't replace it with something irrelevant or annoying is just a plus. I like how they play with the background sounds, but it didn't feel really special to me. Good quality music, able to set the mood, and doesn't stand out, so it's good.
8/10

Characters: A pack of unique characters always does the job in here. Although nothing (except for some doujin-love) is explained about characters, you should've watched the anime before going to this, so no problem with that. SPOILER: I find it rather sad how that love scene was lost because of that so-called cure of allergy.END SPOILER
10/10

Enjoyment: Like I said before, this was a good way for quick laugh. Contractors don't dream and aren't allergic to pollen! I really had some great time watching this OVA. I'm kind of relieved that this OVA didn't contain any relation to the actual progress of the plot. I seem to like the side-stories of the action anime that contain a good amount of laugh.
10/10

Overall: For all of us who have missed DTB, we got what we deserved. An OVA that is just like another episode of DTB, with some comedy aspect in it. It's just like the feeling that I got from Full Metal Panic: The Second Raid OVA. When you miss a serious anime, it's best to remember it with it's funny moments. It's better for you to watch a comedy-based episode rather than a serious one. Watch it.
9/10

Can be summed up as a one-shot sidestory with a healthy dosage of CRACK. You'd have to have some background from the first half or so of the series in order to know what was going on, but most of the events in this episode end up being absolutely useless to the continuum, as they're all forgotten because of a plot device at the end of the episode. Plus, it takes an amusing look at fandom.

Aside from the Story, nothing else has really changed from the series, so I won't be covering Length, Music, Art, or Seiyuu.

I'm not happy that it didn't resolve several ... of the issues of the series. But, overall, it's a nice amusing diversion.

Filler content doesn't necessarily have to be bad content, but this filler really missed the mark. When considering filler content you need to ask yourself if the media you are working with suits the type of filler you are making. A "What-If" filler for example may have been more suitable for a series with this gravity rather than the comedic one we received.

Every attempt at humour is reaching at truly low-hanging fruit, employing only the cheapest gags and most over-used/cliche anime jokes in existence. It contributes nothing to the overall narrative and doesn't even remotely fit within it. The characters are stiff and at times ... totally out of character. Overall it lacks everything that makes the series itself good. Gravity, the sparing use of comic effect at times to keep it from being overly edgy/grimdark, the natural-feeling character interactions.

When people disparage filler content this is exactly the type of episode they are referring to.