[GoNative]

Here is the law regarding possession or distribution of child pornography

Article 7 - Distribution, etc. of Child pornography

1. A person who distributes, sells, lends as a business, or displays in public, child pornography shall be punished with imprisonment with labor for not more than three years or a fine not exceeding three million yen.

2. A person who produces, possesses, transports, imports to or exports from Japan child pornography for the purpose of conducting any of the acts mentioned in the preceding paragraph shall be punished with the same penalty as is described in the said paragraph.

3. A Japanese national who imports to or exports from a foreign country child pornography for the purpose of conducting any of the acts mentioned in paragraph 1 of this article shall be punished with the same penalty as is described in the said paragraph.


So although paragraph 2 touches on possession it is only a crime if they conduct any of the acts mentioned in paragraph 1. So possession in itself is not a crime when it cannot be linked to distribution. You can probably see how child pornographers could make it quite difficult to prove the acts in paragraph 1.