A Little Fall of Rain is one of the many tear-jerker songs in Les Mis. It is a duet found between Marius and Eponine. It takes place on the barricade after Eponine sacrifices her life for Marius, the young man she loves. The love she has for Marius is unrequited. In this scene, Eponine is dying, but in the arms of Marius. This is actually in so many ways the happiest moment of her life: if you think about it, she grew up with unloving, abusive parents who raised her to be a thief and criminal and fell into extreme poverty. She wasn’t shown kindness. Marius ended up being the only person who showed her kindness- that is why she fell in love with him. That is why dying in his arms was probably the happiest moment of her life. That is a huge reason why this scene is bittersweet.
At the same time, there is this level of heartbreak. After all, she is dying and Marius is devastated. Despite how heartbroken he is, he still shows her compassion by holding her and comforting her while she is in pain from the gunshot wound. All that matters to Eponine is that he is with her- not so much the physical pain she is in. Even though her life was dark and tragic, at least in the end, she was with Marius.