Four-Character Idiom · Conviction & Will · Kyojuro Rengoku
Meaning
To press toward a goal with courage, undivided focus, and unceasing diligence. The compound stacks martial vigour (勇猛) with the Buddhist virtue of unbroken practice (精進).
困難を恐れず、勇敢に一心不乱に目標へ向かって努力し続けること。
The Kyojuro Rengoku line
Verbatim from the source article
「昨日の自分より確実に強い自分になれる」
"BUT YOU'LL BE MUCH STRONGER THAN YOU WERE YESTERDAY."
Why it fits Kyojuro Rengoku
The promise that "you can become a self stronger than yesterday's self" is yūmō-shōjin in plain-form Japanese: courage joined with the daily, unsexy work of practice. Rengoku addresses it to the trio, but the doctrine is older than him by a thousand years.
Cultural note
Origin in classical / Buddhist / Confucian tradition
精進 is one of the six Mahayana Buddhist pāramitās (transcendent virtues) — the perfection of diligent practice.
Sources
- デジタル大辞泉 — 勇猛精進 (dictionary)
- 精選版 日本国語大辞典 — 勇猛精進 (dictionary)