I have not watched that anime so don’t know the example you saw. I also was not into journal use when I was shooting more actively. I journaled other stuff and then changed formats as I went. So here’s some brainstorming.

Go do it for a while, and let yourself discover what you want in it, and then format it nicely as you figure it out. Put all your shooting data if you want, then decide after whether you want to pare down how much you write because it’s also in the metadata in the file. With digital it’s less important to write down the exposure values for each frame, so you could concentrate on trends for outings.

If you work with lights (continuous or strobe) sketches of the setup. Others might just back up and take a photo of the setup, or sit where the subject is and shoot outwards to see what the subject would see (or ‘see’ in the case of an object).

Ideas for notes outside of shooting: things you want to keep an eye out for because you didn’t notice them at the time (distracting objects, for example). As you read/watch learning material, takeaways and things to try, and then after when you decide how you felt about the techniques. Lessons learned for when you mess up, such as packing lists or checklists so you don’t drive somewhere short a critical piece of equipment.