How to use こと is correct. But example sentence(?) is not correct. いっしに→ひっしに hisshini こなたのことを→あなたのことを anatanokotowo みつけよう。 is correct. Your sentence is not unnatural. Japanese people understand this meaning. This words is very romantic!! If you say this words for Japanese, they might throb^_^ Does that make sense. Sorry...I'm not good at English(*_*)