このため彼は命をうしなった。

this (something or someone close to the speaker (including the speaker), or ideas expressed by the speaker)

good; advantage; benefit; welfare; sake; purpose; objective; aim; consequence; result; effect; affecting; regarding; concerning

he; him; his; boyfriend

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

life; life force; lifetime; lifespan; most important thing; foundation; core; paired tattoos of the "life" kanji on the upper arms of a man and woman (indicating unwavering love); fate; destiny; karma

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 lose; to part with