Mail yahoo co jp
You're looking for the Yahoo Japan email service!
The Yahoo Japan email service is operated by Yahoo Japan Corporation, a Japanese internet company. The service is known as "Yahoo! メール" (Yahoo! Mail) in Japan.
Here's the official website for Yahoo Japan email:
You can access your Yahoo Japan email account by going to this website and logging in with your email address and password.
Note that the Yahoo Japan email service is only available in Japanese, so you may need to use a translation tool or browser extension to navigate the website if you don't speak Japanese.