Offers offline viewing for Mega Fan subscribers through their mobile app. Digital Purchase (Permanent Download):

Available for streaming and offline download with a standard plan.

If you're looking to download (IWGP) for offline viewing, there are several official ways to do so through streaming subscriptions and digital purchases. Where to Watch and Download IWGP

This response uses data provided by Google's Knowledge Graph Ikebukuro West Gate Park (TV Series 2020) - IMDb

You can legally download episodes for offline use through the following platforms:

Episodes are available for purchase (typically around $2.99 per episode) to download and keep.

Offers episodes for purchase and download in select regions. Why Watch Ikebukuro West Gate Park? Google Watch Action Data