I can think of at least half a dozen songs by Japanese pop rock singer LiSA that deserve the spotlight more than Shirushi, but I saw this live performance last night and can't get it out of my head.
First thing to note: for a live performance, it's very true to the studio version, at least for the first 90% of it. Second, she fills stadiums in Japan, but as far as I know, has never toured in the US or Europe. Japanese bands don't command such big audiences abroad, so they tend to stay home, and the rest of the world is poorer for it. Third, at the end of the performance, she legitimately breaks down in tears. The band tries to cheer her up with a more upbeat tune, and she tries to hold it together, but ultimately leaves. I'm not sure if this was the last song in her set, but she clearly needed a break after performing it.
The whole song is in Japanese, so if you don't know Japanese, you might not understand why she cries at the end. But, you might if you watched some anime that is in English. LiSA got her start in anime music with the anime series Fate/Zero and her song Oath Sign, but it was Sword Art Online and her song Crossing Field that made her famous. She made the opening theme for what would be, for a few years, the biggest anime series out at the time. The ending theme was done by Haruka Tomatsu, who voiced the main girl in Japanese. (The voice of the main girl in English didn't sing anything for the series, but she voices the protagonist of Cyberpunk 2077 opposite Keanu Reeves and Idris Elba, so not too shabby!) For the second and third arcs (end of first season, beginning of second season), they had two other singers do the openings and endings. One did both endings, the other did both openings, and they were good. For the fourth arc, the end of the second season, they brought back the first two singers, but they switched them around. Haruka Tomatsu got the opening, and LiSA got the ending, and that ending theme was Shirushi.
Both of them poured their hearts into their respective themes. Tomatsu, because the arc was focused on the character she voiced, and, to be absolutely clear, we're talking about the adaptation of Sword Art Online, Vol. 7, Mother's Rosary, the peak of the series to date (there are about 25 volumes now). If Mother's Rosary was its own, standalone anime, it would either be my favourite anime, or it would be top 3. As it is, it's a big part of the reason I rate Sword Art Online as high as I do.
Anyway, I'm pretty sure LiSA knew the story before writing the song. The book isn't long, and while I don't understand Japanese and I don't know what she's actually singing, the song will forever be tied to that story, and if you knew the story, you'd probably understand why, however many years later, performing the song brings the singer to tears.
What I will say is that while the main guy is off doing main character stuff, the main girl hears about this woman challenging anyone to a duel, and after more than 50, she hasn't been defeated yet. She's quickly becoming a legend, so the main girl decides to head on over there and see what all the fuss is about. She faces the duelist in battle, and gives it her all, but the duelist calls a draw when she's down to just a sliver of life. (The whole story takes place in a virtual reality video game. They can leave at any time, and dying in the game, unlike in the first arc where it's a death game, just means they start over in town.) Then takes her and they run off together. The duelist tells the main girl she's actually recruiting for a quest. The quest isn't that important. What is, is when the duelist calls her "sis" a couple times, catches herself, and leaves. The second time, she stays gone, and everyone tells her to not pursue it. But, her boyfriend is a national hero, and a hacker, so he's able to track her down in the real world. Then he tells her to stay away, but she can't. And that's when shit goes sideways.
In addition to that, the main girl is dealing with her mother, in real life, who is telling her that online connections don't matter, and she needs to focus on her school and professional lives. That story plays out to a very satisfying conclusion, inspired by the events of the first story.
The show (I mean, those seven episodes that adapted the book) was excellent, but somehow, the book was just a little better. I didn't physically read the ink on paper; rather, I had Cherami Leigh (who voices the main girl in English) read it to me, via the audiobook. There's ever so slightly more to the story in the book, though I wouldn't say the show missed anything important. I wonder if she was able to make it through the reading without shedding a tear. I certainly wasn't, and I wasn't voicing the characters.
If you have Crunchyroll, or some other service that carries it (Netflix used to, not sure if they still do), do yourself a favour and watch the fourth arc of the anime. You don't have to watch the stuff that comes before, though, it can be helpful as background. Maybe watch a recap of the first season on YouTube. Anyway, go to the second season and watch the 18th episode, Forest House.
Maybe someday, someone will adapt that book into a standalone film, somehow. I'd love to see how that looks.
And on a much lighter note, the author wrote a prequel to Mother's Rosary in Sword Art Online, Vol. 22, Kiss and Fly, which is a collection of short stories. It starts with Yuuki, the duelist from Mother's Rosary, playing a different game. They call it Serene Garden, but it's basically Animal Crossing in VR. Except for the name, that's literally exactly what it was. Plus multiplayer. There's... a bit more to it than that, but you should not read the prequel (it hasn't been animated yet) before reading/seeing the main story, since, you know, it kinda gives up the main story's twist, since it assumes you know it.
So hey, there's your homework. Read Mother's Rosary or watch the anime adaptation and get absolutely wrecked (thereby learning why LiSA breaks down in tears at the end of the live performance)... or go play some Animal Crossing and heal your soul while you work for Bells to pay the capitalist swine raccoon for your home loans... or just go fishing and bug catching.