"Hanamizuki" (Dogwood) was the second song by Yo Hitoto（一青窈）that I became interested in after her debut single, "Morai Naki" (もらい泣き...2002). Not only did her 5th single have that sort of melody which got me in a more contemplative mood, the original music video showed that close-up of the singer's performing style. She just has that way of expression with her face and hands that was simply distinctive. I actually caught her last night on an episode of "Kayo Concert" where she did a cover of an old Duke Aces' chestnut, and once again she revealed some of that Hitoto balletic elegance in her moves.
According to the article on the song in J-Wiki, the singer was inspired to write the lyrics to "Hanamizuki" from an e-mail that she had received from a friend in New York at around the time of the September 11th 2001 terrorist attacks. It took Hitoto about a week to get it all down on paper, and apparently an early draft of the ballad included words like "terrorism" and "shotgun", which, considering the soft and comforting tone, would have been somewhat jarring to my ears. Fortunately those words were excised, and the lyrics turned out to be those words of comfort and reassurance as if Hitoto were personally addressing her friend. As I've mentioned before, I'm not much of a lyrics guy so with me, the singer's face and gestures were enough to convey to me that she was telling such a story. As with "Morai Naki", the composer was Tatsuro Mashiko（マシオタツロウ）.
Another piece of trivia I got from J-Wiki was concerning the title in that Hitoto probably got it from a place that she used to visit frequently as a student, Dogwood Plaza. I could probably speculate that it was her home away from home. Released in February 2004, "Hanamizuki" peaked at No. 4 and ended the year as the 30th-ranked song. However, its feat didn't end there. It became one of the longest-lasting singles on the charts, staying there for 125 consecutive weeks, and finally ending up as the 6th-ranked song of the year in 2007. That year, she performed the song at the Kohaku Utagassen accompanied by her old friends from her university club as they all also conveyed the lyrics in sign language.
In the decade since the song's debut, it's gotten a lot of cover versions by other singers such as Ryoko Moriyama, Hiromi Iwasaki, Hideaki Tokunaga (as shown above in a duet with Hitoto) and most recently, Akina Nakamori in her 2015 release "Utahime 4"（歌姫４）.