“To become an adult” in Japanese
Short answer
To become an adult in Japanese is “大人になる” (otonaninaru). Full meaning: to grow up, to become an adult.
Other ways to say “To become an adult” in Japanese
大きくなる
ookikunaru to grow up, to become an adult; to become big, to grow in size
一人前になる
ichininmaeninaru to come of age, to become an adult, to become fully qualified, to stand on one's own
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