WataMote - Sokora no Kigurumi no Fuusen to Watashi (5th ED)
WataMote is a painful-bittersweet story about an antisocial, socially awkward, and delusional girl. It's an anime difficult to watch at times but manages to cling on like an emotionally attached significant other you want to be with despite the hardships. The picture used in the video sums the story and character pretty well.
After watching the OVA that got subbed today, one thing led to another and I was piqued by the ending song that stuck to me when I watched the original series. This played at the end of episode 11, following a sweet moment, with a rarity of 1 in a million, in the bittersweet life of the MC. The song starts off like a Christmas song then gets warm and fluffy like the spring air that spins and spins into a summer memory. It's very well-matched and gives the MC's life a glimmer of warmth - that she is not all that lonely and people notice her.