Normally, I wouldn't translate 鎧袖一触 as 'Beat hands down' for Kaga's lines (even though it can translate as that), but it works really well with the rest of the joke.
Note: Tenryuu is hearing 鎧袖一触 as 外周一色 (same pronunciation) meaning something like 'All inside the circumference' or 'Single-coloured border' depending on which meaning of 一色 you want to take.
Here it is!They will be beaten hands down.
No need to worry.
Attack lineBeat hands downAh... That sea area? I shall beat that hands down.
1400 time notificationTo defeat an opponent with ease.Beat hands down... Beat hands down...The heck? 'Hands down'?flip-flapBeat hands down/biːt hændz daʊn/
【鎧袖一触】Gaishuu Isshoku
Literally, single touch by an armoured sleeveOriginating from the expression that an enemy instantly falls after being lightly brushed by an armour's sleeve
This is for the Japanese expression