彼はきっと来る。

he; him; his; boyfriend

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

surely; undoubtedly; almost certainly; most likely (e.g. 90 percent); sternly; severely; having no slack; rigid; stiff; tight; suddenly; abruptly; instantly

to come (spatially or temporally); to approach; to arrive; to come back; to do ... and come back; to come to be; to become; to get; to grow; to continue; to come from; to be caused by; to derive from; to come to (i.e. "when it comes to spinach ...")