Prime Minister Abe Shinzo is reported to have said that "Japan cannot be a "normal state" until Japan has a fully functional armed force." There are reports that majority of the Japanese are not in favor of amending Article 9. Other than the apparent nationalist pride, is there any other factor in play?
The biggest reason is that without a meaningful military of its own, Japan is dependent on the USA for its security. During the cold war this was a reasonable position, but increasingly in the post Soviet Union world, Japan's interests and the USA's interests are not necessarily aligned. What might be an existential threat to Japan (e.g. North Korea's missile program) might be an acceptable strategic situation to the USA.
Though President Trump"s tenure in office may have strengthened this opinion - I doubt South Korea or Japan has much confidence that he would back them up in a crisis - it predates him and will continue after him. Many Japanese politicians understandably think that Japan ought to be responsible for its own security, and free to act on its own to ensure that security, rather than being reliant on the USA deciding that defending Japan is worth the cost, rather than an acceptable price to pay.