I spent months researching this before my first submission, and honestly the biggest mistake I made early on was thinking I could just write in English and they'd be interested. Japanese publishers expect the script format to follow their industry standards from the very first page. That means you need to use the proper four-panel manuscript paper layout digitally, with clear separation between dialogue, sound effects, and panel descriptions written in Japanese. I use a software called ComicStudio now, but some folks start with Clip Studio's story editor. The trick is making your visual descriptions incredibly concise—they're not prose. Every line should paint a clear image for the artist. If a panel description runs longer than two sentences, you're probably over-explaining and slowing down the pacing.
Another thing that's easy to overlook: you need to study the specific magazine you're targeting. Is it 'Shonen Jump', known for fast action and clear good-vs-evil themes? Or something like 'Young Animal' with more mature, psychological plots? Your script's tone, chapter length, and even the ratio of action to dialogue should match that magazine's house style. I sent a very quiet, character-driven script to a battle manga magazine once. Learned that lesson fast. Include a short, compelling logline and character profiles upfront, but keep the artist's workload in mind—don't design a main character with impossibly detailed armor in every panel.
Networking helps more than we'd like to admit. Getting feedback from Japanese artists online, or even submitting to contests like the ones Silent Manga Audition runs, can get your work in front of editors indirectly. Sometimes a fresh, foreign perspective is a selling point, but it has to be delivered in a package they already understand how to process. My last script got a second look because I framed it with a classic 'nen' rivalry dynamic but set in a cyberpunk world they hadn't seen before. It’s about speaking their language, both literally and structurally.