What is Your Lie in April about?

Your Lie in April is a manga and an anime about friendship through music. The protagonist Kosei Arima is a very talented piano prodigy who goes through a mental breakdown from the pressure of performing and becomes deaf to the sound of his own piano. The world becomes monotonous and depressing until he meets Kaori Miyazono, a free-spirited violinist who reminds him of how to play music freely again. However, Kaori suffers from anemia and often has to go to the hospital. Despite this, the two often play together and Kosei falls in love. Kaori passes away soon after and leaves a letter for Kosei explaining how she loved him back and his piano playing. Kosei uses this as inspiration to get back into music and play freely once more.