毫不在乎: not to care a snap [pin; damn; dime; hang; curse; cuss; farthing]; completely unperturbed; disregard…; do not mind or care at all; make nothing of…; not at all perturbed; not care at all;
我只在乎你: i only care about youi only mind youonly care youonly you in my mindtoki no nagare ni mi o makasetoki no nagare ni mi wo makasetokinonagareni mio makaseyou are the only one i care for