I don’t really visualize them at all, personally I don’t find it helpful. I don’t have any idea what Koichi, Gouichi, Mrs. Chou, Jourm, etc look like. Other than maybe Chou and Gou are just old. They are personalities to me rather than visualized things. Except for Hard Gay who is a real person so that one I can actually pull visualized things from. Luckily not cursed with aphantasia but I am not often actively making the scenario appear in my head. I’m treating them like really tiny stories and just recalling how the story went with piecing radicals together. I feel like it would be way too much brain power to think of 2000 kanji and 10000 vocab brain-visualized scenarios each rather than short (completely nonsensical) stories. Stories of which eventually I completely forget because the words in front of me just magically are the word I know over time.
For example my brain process goes like this, an easy kanji for example. The town 「町」 mnemonic. I’d start with just the radicals formation (two, rice paddy and street) and I will focus on just those aspects. I shove those into the radical part of my brain and try to just remember those two things in combination and what they mean together.
The supplied default mnemonic being “When you see both a rice paddy and a street in the same place, you have the makings of a whole town!” So when I see the Rice Paddy + Street radicals, it forms a town. In my head what is being visualized, specifically subconsciously is actually a bustling Japanese street, completely illogical to the rice paddy. So I just ignore what my brain is trying to push at me “visually” in my head since it’s vague an unhelpful in most cases for me personally.
Okay so cool, there’s Rice Paddy and Street, that’s a town because what town isn’t complete without a rice field…? What do I do with this now, what is so interesting about this town. Oh right it’s Mrs. Chou causing ruckus in the town, again. Maybe she is digging up the rice paddies or something.
This all becomes mostly irrelevant because by the time you’ve burned it, radicals for the kanji aren’t being relied on anymore, and the short story recognition is instant if needed at all.