Sites to read manga in Japanese?

Where do I find sites to read manga in Japanese? If there’s a single site with a great catalogue I don’t mind paying for it, I just don’t wanna pay for multiple sites. Preferably a website and not an app.

I’d like to start off with berserk, 20th century boys etc. I know of sites with free stuff but they’re all the most obscure manga ever, I’d like to read more mainstream stuff

And if there’s no such resource, piracy is also okay I guess (you can PM links if it’s against the rules here).