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to lose sight of (one's companions); to stray from
to miss (one's chance to ...)
「逸れる」 has another reading with different meanings.
弾が的から逸れて後ろの壁に当たった。
The bullet missed the target and hit the wall.
彼の視線が一瞬だけ逸れたのを見た。
I saw his gaze wander for just a moment.
話題が逸れたので元に戻しましょう。
The topic strayed, so let's get back on track.