Reputation: I am unfortunately, not too familiar with Noriko Hotta. I suppose she doesn't illustrate too much for the Pokémon TCG, so that's all I can really say.
Subject: Mime Jr. can do with a little more texture. Right now, it has that plastic feel that CGI will make on default; I've seen good CGI texturing from illustrators like Kent Kanetsuna (his later work, at least) and 5ban Graphics. As for the pose, I like it. Despite not much movement taking place, it's still dynamic in that Mime Jr. is in the middle of doing something and is physically pulled by momentum in its movements. You can tell from the asymmetric foot positioning and how the arms are positioned at a slightly different angle from the torso. I also like the lighting here; you can tell the light source is the Lost Zone portal. What I don't like is Mime Jr.'s expression. It doesn't look threatening or cute. Rather, because it has those half-closed eyes and a small frown, it looks more like it's under the influence, so to speak. It doesn't seem like the expression something would have when harnessing a Lost Zone portal. Why does it look like this? Is it in a trance? Is it being manipulated by someone or something else? Does creating a Lost Zone portal put one in a nontypical mental state? There is nothing depicted on this illustration that would help answer that.
Background: Like with Mime Jr., the lighting seems to be coming from the Lost Zone portal. This is nice, as the background matches with the subject and is not something just put on after drawing the Pokémon (which some illustrators are guilty of, namely Ken Sugimori). It gives you the impression that Mime Jr. is actually there. The background is also appropriately creepy: It contrasts Mime Jr.'s bright colors with dark and dull greens and browns and is really dark behind Mime Jr., seemingly neverending. The trees have twisted branches and roots evoking the haunted forest look; it's almost as if the branches are going to move by themselves like arms. Moss grows rampant on the trees, suggesting the climate is humid and cold, just as you'd expect a creepy place to be like. Basically, it's a forest where if you step in, you don't know what's going to be there--and even the colorful cuddly Mime Jr. can summon Lost Zone portals. However, you can see the bright sky at the upper-left corner, perhaps representing hope.
Others: The Lost Zone portal has such detail, it feels like there was just as much time making the model for the portal as there was for Mime Jr. and for the background, if not more. The purple swirls, the white light emanating from the center, and the blue aura around it come together for something that looks truly otherworldly. None of the colors interfere with each other, which is a mistake very easy to make. The lightning bolts spread evenly throughout the illustration, giving the image balance (just as how Mime Jr. is slightly off center to the right and the Lost Zoe portal similarly off center to the left). However, the sparks coming out form the portal seem to be restricted to a particular latitude line around the sphere. It's not like a plasma ball where it can come out from anywhere. The Lost Zone portal would've looked perfect if the sparks came out from seemingly random points on the sphere.
Overall, I would give this illustration a 7 out of 10. The strongest points are the feelings of uneasiness it provokes and the detailed background and Lost Zone portal; the weakest is the texturing on Mime Jr. and the strange expression. (All other Pokémon from this set have an easily interpretable expression, but not Mime Jr.)