Ludicrous speed!
迅速果断
jin.soku.ka.dan
Literally: fast – fast – fruit – sever / decide
Alternately: Quick and decisive action. Bold moves made without hesitation.
Notes: For synonymous phrases the order of the elements may be reversed as 果断迅速, or 断 may be replaced with 敢 (kan, “daring”).

The joke is that this little nameko mushroom [source] enacts a 迅速果断 to put up an anti-rain charm instead of just bringing the laundry inside.