noun
feeling like lovers; lovey-dovey mood
Describes the atmosphere or emotional state of being like a couple, often used for new or budding relationships.
二人はまだ付き合っていないけど、恋人気分を味わっている。
They aren't dating yet, but they're enjoying the feeling of being lovers.
デートの帰り道は、すっかり恋人気分だった。
On the way home from the date, it felt just like we were a couple.
Compound of 恋人 (lover) and 気分 (feeling, mood). The exact origin is uncertain, but it likely emerged as a natural expression for the romantic atmosphere between two people.