Tonari no Shugoshin

After losing her parents when she was young, Rio has been supporting herself and her brother. Rio believes that it's useless to rely on others. One day, she buys a trump card of the jack of club, modeled after Sir Lancelot, believing she could gain good money auctioning it off the internet. That night she meets Sir Lancelot in her dreams, which recur every time she sleeps. When Yuuki-kun asks her to go out with him and nearly kisses her, Lancelot suddenly appears out of nowhere and says he has come to save her?!

(Source: MangaCity)