君は彼女を助けなければならない。

you; buddy; pal; monarch; ruler; sovereign; (one's) master

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

she; her; her; girlfriend; sweetheart

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

to help; to save; to rescue; to give relief to; to spare (life); to reinforce; to promote; to abet