That Time I Got Reincarnated as a Slime: Visions of Coleus

This takes place between Season 1 & Season 2. A 3-episode "arc" where Rimuru tries to resolve a dispute within a kingdom but uncovers a conspiracy. Sound familiar? It's basically the plot of Scarlet Bond movie but paced better. Story-wise, it's been done before within the series, even down to the tropes and lack of stakes or tension. Honestly, it's just something they put out to tide people over till the next season's release and to give an "early" look at Luminous and Violet for fanservice reasons. So it's no secret that Fuze (the author) have been making spin-offs left and right to milk the popularity of theseries as much as possible as he's nearing the end of the Light Novel. This is one of those. Are you missing out on anything important by not watching this? No, but you still might enjoy this if you're one of those people who would consume anything regarding this series.

My appreciation for this side story is influenced by my seeing the theatrical movie, which was also a side story. This ONA and the movie have similar plots points, sickly female royal cursed by a shady court physician and a brotherly rivalry, stands out the most. However, my choice would be this three-episode ONA. It just has better pacing and tighter plotting, without the need to cast cameos from other series regulars who do not have a major role in the story and thus making for a clunky and overdone mess. For Tensura fans, this is something to tide you over waiting for the next full seasonof the main story. Don't expect too much and enjoy the show.

Visions of Coleus is a short story that happens between the first and second season of 'That time I reincarnated as a slime'. It's not crucial to the main story but it does give a bit more information on some elusive characters and explore another nation so it is worth watching in the main series. The story is about Rimuru going to another nation to attempt to gather information about a possible civil war. The story isn't super impressive or anything but it's fun to watch regardless. The characters are mainly just rimuru and and locally relevant characters with actual significant characters occasionally coming up.The characters seem just fine, it's just three episodes and enough information is given to understand the characters but not much more. The animation, voice acting and sound are all fine and are good enough for the story. Overall I'd recommend watching this since it does add to both the worldbuilding and characters in the slime world. It's probably best to watch it between the first and second season but watching it afterward doesn't matter much either.

TLDR : All in all an 8/10 for Slime Isekai lovers ig. I Haven't read the source materials or anything but if you loved/liked the previous seasons of Slime Isekai then you will definitely enjoy these 3 episodes. But the question does rise why they are animating such unrelated filler material type content when they can spend the same resources to just continue the proper main storyline. We get to see Rimuru, soei and benimaru in action and glimpses of Rimuru's wolf Ranga. Good pacing and a more or less well coherent story that spans 3 episodes well. The new characters introduced do seem one dimensionaland not well fleshed but they serve the purpose well for a 3 episode story . One point of concern was that the power scaling was a bit off in my personal opinion with normal looking demon being considered close to that charybdis clamity and rimuru actually having to think twice before going to combat. Also benimaru and soei felt strangely underpowered. Like that OPMCness was a bit lacking.