彼に任せよう。

he; him; his; boyfriend

at (place, time); in; on; during; to (direction, state); toward; into; for (purpose); because of (reason); for; with; by; from; as (i.e. in the role of); per; in; for; a (e.g. "once a month"); and; in addition to; if; although

to entrust (e.g. a task) to another; to leave to; to passively leave to someone else's facilities; to leave to take its natural course; to continue (something) in a natural fashion (without particular aim); to rely fully on one's (full strength, great ability, long time taken) to get something done