At this stage, the theme appears to only be available in Asian countries. Though we have not been able to check every country as of writing, we can confirm LINE users in the United States and Australia are unable to purchase the new theme at this time.
- Sources
Pokémon Pixel Art – LINE theme | LINE STORE
Pixelated Pokémon star in a LINE theme! Invite these adorable critters into your chats. Updates supported for 180 days after sales end.store.line.me