Enthusiasm for a group outing with 乗り気

Vocabulary Explanation: Enthusiasm with 乗り気

Kikuchi asks Futaba out. He says if she prefers, they can invite their friends along as well. After school, Futaba brings it up with her friends. Yuuri says she’ll go if Kikuchi’s friend Uramiya is there.

悠里(ゆうり):: 「でも双葉(ふたば)ちゃんが乗(の)り気(き)じゃないんなら…」; “But if you're not interested...”; Literal: “But if Futaba-chan's riding spirit isn't there...”
双葉(ふたば):: 「うーーーん」; “Mm...”

Key Points

1乗(の)り気(き) means interested or up for it

Yuuri is checking whether Futaba actually feels willing to go.
The negative じゃない means “not interested” or “not into it”.

2んなら is casual のなら

乗(の)り気(き)じゃないんなら means “if you are not interested”.
The contracted form fits a casual conversation.

ちゃん is an affectionate, informal suffix attached to names, used mainly for children, close friends, and family members.