Per our policy, one can do some checks with Commons:De minimis#Guidelines:

• the image is categorised in relation to several Pokémon characters
• Pokémon are referenced in the filename and the description.
• Some images are used to actually illustrate articles about a Pokémon character.

These bullet points make for that "the file containing copyrighted work X is less likely to satisfy de minimis" per our guideline.

In COM:DM Japan, there's a reference to a copyright law amended in 2012. Here's the pertinent part as written on the reference page: "Article 30-2: When creating a copyrighted work of photography, sound recording or video recording, other copyrighted items that are incidental subjects of the work because they are hard to be separated from the item that is a subject of the work may be copied or translated along the work being created (only if they are minor components of the work being created). However, if, considering the kinds of the incidentally included works and the manner of the copying or translation, it unfairly is prejudicial to the interest of the copyright holders of the incidentally included works, they may not."

These Pokémon images cannot fulfil this "incidental" clause, as they are objectively prejudicing the opportunity of Game Freak / Nintendo to license Pokémon illustrations to potential customers wanting to illustrate the characters.