One Piece -dub- Episode 373 -

Next sentence: "This allows viewers who may not be fluent in Japanese to still enjoy the episode with ease." "allows" can be "enables|grants|permits". "viewers" again could be "spectators|watchers|audience". "fluent" is "proficient|skilled|versed". "enjoy" might be "appreciate|relish|take pleasure in".

Alternatively, for "catch up on the action", perhaps use "review the action", "follow the action", "get caught up on the action". The user wants to replace each word, so break into individual words.

epic → legendary

Original text: "is a great opportunity to catch up on the action and join the Straw Hat Pirates on their epic journey."

Replaced words:

The proper noun "Straw Hat Pirates" is skipped.

"Their epic journey" — "grand adventure", "momentous voyage", "legendary quest". One Piece -Dub- Episode 373

on → while