I found a way to fix the ugly font, in case anyone has the same problem.
Step 1: Use GARbro to extract the "patch.xp3".
Step 2: Copy "Noto Sans Mono CJK JP Bold.otf" to the "image" folder 5 times. Then rename all of them to "font_10.tft", "font_16.tft", "font_24.tft", "font_40.tft", "font_50.tft".
Step 3: Repack the new "patch.xp3" using Garbro's Create archive with Retain directory structure. Then copy it to the game folder.