Maybe it was a mistake letting you drink alcohol. It didn't take a lot to get you drunk, and you acted so different when you were. Next time he hoped Francois would tell you no to alcohol and serve you something else instead. Sure, you acted way older than you were, but you acted a little crazy when you were drunk.
Ryusui had his arm wrapped around your waist so you wouldn't go off and do something. During this time you said so many things to him, like how you loved him, and wanted him, and things like that. When he's told you he loved you multiple times when you were sober and you got awkward and denied him, and when he was the one drunk and he acted so loving, you told him to sober up. Why couldn't you just believe he was in love with you?
He really wished you were sober, he couldn't believe what you were telling him right now. He also wished that you would believe him when he said he loved you, that he wanted you, that you meant a lot to him.. But you always told him you didn't believe him, but why would he lie when it's so clear he's in love with you?
"Just stay here." he said as he squeezed his arm around your waist a little bit tighter. He then pushed over a glass of water to you.