Mutual love; when two people like each other (romantically).
彼女と彼はついに両思いになった。
She and he finally became mutually in love.
告白したら相手も同じ気持ちで、二人は両思いだった。
When I confessed, the other person felt the same — the two of us were mutually in love.
クラスの噂ではあの二人は両思いだそうだ。
Rumor in class says those two are mutually in love.