back seat (seat)

baggage, luggage / unwelcome burden

the rear, the back or posterior part

seat

he / distal demonstrative, something far off removed from both speaker and listener: that / boyfriend

distal demonstrative, something far off removed from both speaker and listener: that, yon / particularly, male personal third person pronoun: he / by extension from he: boyfriend

he; boyfriend

to put, place, set / to leave (something) / (following a て-form verb) to do something in advance as preparation / (following a て-form verb) to do and keep in that state

ejector seat

(colloquial) current boyfriend