"to enter the head": for learning to stay in one's head

eyeball

a type of くす玉 (kusudama, “decorative ball”) that splits open to reveal a banner, confetti, or balloons

a tamarin

(idiomatic) to be sharp; to be keen; to be on the ball; to have a mind like a steel trap; to be clever

(idiomatic) to get mad; to be highly offended; to get pissed off; to get angry; to lose one's cool

iridescent; having different colours when the angle of view or illumination changes / ambiguous or vague; using weasel words

to use one's head

(slang) a forgetful person

a deposit (oney given as an initial payment) or down payment (payment representing a fraction of the price)