Ecchi Shiyou means “let’s do lewd things” or “let’s fuck” in Japanese
It all depends on how you say it, if said wrong you’ll be in jail for attempted rape. If you say it the right way they’ll drop dead and open up to you.
Joji saw a lovely girl on the train one day, he had the courage to walk up to her and say with all his heart “Ecchi Shiyou”, later that night he became JOJO because of the extreme manliness.
It's a genere in japanese anime and manga that reffers to erotic but not abruptly sexual content. It can show full to partial nudity, including nipples, cameltoes, panty flashing, grabbing boobs, but never exposed genitals, and is often displayed in a humoresque way. The term comes from the japanese pronunciation of the letter "H" (pronounced "eh-chi") as in Japan erotic content is rated "H" while in the rest of the world its more commonly rated "X".
Outside of Japan it's easier to understand Ecchi as softcore, non-sexual and erotic and Hentai as hardcore pornography.