Taken from this post on the Metroid Construction forums: http://forum.metroidconstruction.com/index.php/topic,2230.msg45819.html?PHPSESSID=37004dc2618ed9b5918bf408b09033d3#msg45819

The Japanese version of Metroid Fusion had some changes done compared to the North American and European releases of the game. The two most notable changes were the inclusion of a Hard difficulty mode and the extra ending images. These IPS patches will force the Japanese version of the game to display text in the language of the IPS patch chosen.
Further changes made can be read on The Cutting Room Floor: https://tcrf.net/Metroid_Fusion#Regional_Differences

As the Japanese version is based on the European release of the game, it is possible to force other languages to be displayed instead of Japanese Kanji or Japanese Hiragana.
When choosing the option "オトナむき（漢字あり)" the difficulties will be displayed in English.
When choosing the option "コドモむき（ひらがな)" the difficulties with be in the same order, but instead listed in Hiragana.

fusionj-mod-forceeng.ips will change the game's language to English.
fusionj-mod-forceesp.ips will change the game's language to Spanish.
fusionj-mod-forcefra.ips will change the game's language to French.
fusionj-mod-forceger.ips will change the game's language to German.
fusionj-mod-forceita.ips will change the game's language to Italian.

Database match: Metroid Fusion (Japan)
Database: No-Intro: Game Boy Advance (v. 20180816-092117)
File/ROM SHA-1: 5D21C668BAA84DA4A5B745BE56809BB277F947A3
File/ROM CRC32: 817A7E9E