Somber adjective – Being without light or without much light. Joyless is a synonym for somber in sad topic. You can use "Joyless" instead an adjective "Somber", if it concerns topics such as happy. Nearby Words: sombre, somberly
The titular girl is presented as looking from the lonely protagonist's dreams, and in fact, she turns into the main source of light in his otherwise joyless and somber life, also becoming his Love Interest.