TV Tokyo originally broadcast the Pokémon animated series in Japan.
The series premiered on TV Tokyo on April 1, 1997, beginning with “Pokémon, I Choose You!” It was produced by a partnership involving TV Tokyo, MediaNet, and Shogakukan Productions, with animation by OLM. The program was designed as a television expansion of the Game Boy games.
TV Tokyo is a Japanese commercial broadcaster and part of the TX Network. The Pokémon series became one of its most important long-running programs, helping connect the games with television viewers, merchandise buyers, and later film audiences.
International broadcasts used different networks and schedules. For example, the series reached the United States through first-run syndication in 1998 and later became associated with Kids’ WB. Those international homes can make the original Japanese broadcaster easy to misremember. The question refers specifically to the first Japanese television broadcast, not a later overseas channel.