This reminder is also listed on the web page of the Ministry of Foreign Affairs.
"Although it seems that some passengers are kept in tans etc., if you keep them with clothing insecticide for a long time, the passport laminate will change color due to insect repellent effect Since there is a possibility, please do not keep with the insect repellent.If you are traveling on a passport where the laminate is discolored it may cause problems in the entry and departure examination. "
Many people did not know, how to store passports.
Let's keep it separate from the insecticide for clothing so that there will be no problem in immigration review when saying "When traveling abroad!"