These tags are recommended to be used on all images:

long hair, aqua eyes, eyelashes, blue hair, green hair, aqua hair, multicolored hair, otoko no ko, flat chest

These tags are used to create his regular outfit (if you wish to create a different outfit, it may be helpful to put these tags in the negative prompts):

poke ball print, spiky yellow jacket, blue and red striped scarf, light blue pants, blue boots, blue mittens

Other useful tags:

scarf over mouth, covered mouth