Pokémon Detective Pikachu was released in Japanese theaters on May 3rd, 2019 and it made 457 million yen on 317,000 ticket sales for Saturday and Sunday. For the entire 4 day weekend, it brought in 948 million yen (approximately $8.6 million USD) on 676,000 ticket sales. This was enough for it to place 3rd in box office sales for that weekend behind Detective Conan: The Fist of Blue Sapphire and Avengers: Endgame.

Ticket Sales - Weekend of May 4th, 2019 to May 5th, 2019:

Rank	Previous Rank	Movie Title	Distributor	Theaters	Weeks in Theaters
1	2	Detective Conan: The Fist of Blue Sapphire	Toho	363	4
2	1	Avengers: Endgame	Disney	365	2
3	-	Pokémon Detective Pikachu	Toho / Warner Brothers	349	1

Source: https://eiga.com/ranking/