猫が the cat, acting 魚を the fish, acted on 食べている is eating のを bundles that into one noun 見た saw

I saw the cat eating the fish. のを is the hinge: it turns the whole first clause into the thing that was seen.

You know every word. The sentence still doesn’t come together.

A dictionary gives you five definitions and leaves you to guess how they connect. Kotoba Lens takes the sentence apart instead: which chunk is doing what, which particle is doing the work, and why the order means what it means.

Open Kotoba Lens

Start with a sentence you got stuck on.

Open Kotoba Lens

What you get once you’re in

Structure, not just definitions

Every chunk is labeled with the job it does in the sentence, so a long sentence becomes a handful of parts you can actually hold in your head.
Hear it the way it’s said

Natural speech for the whole sentence or any single chunk, at normal speed or slow enough to follow the pitch.
Keep what you worked out

Turn a sentence you fought with into flash cards and scheduled review, so the grammar point sticks instead of being re-learned next month.

You know every word. The sentence still doesn’t come together.

Open Kotoba Lens

What you get once you’re in

Structure, not just definitions

Hear it the way it’s said

Keep what you worked out