Departure; setting off on a journey or embarking on a new stage of life — a noun often used in both literal and figurative/ceremonial contexts.
彼は海外留学のために旅立ちの日を迎えた。
He reached the day of departure for studying abroad.
新しい人生の旅立ちを祝ってパーティーを開いた。
We held a party to celebrate the start of a new chapter in life.
朝早く駅で友人の旅立ちを見送った。
I saw off my friend's departure at the station early in the morning.