秋桜 aka COSMOS aka Kosumosu from the youtube comments I read. But what is cosmos? What is kosumosu? Thanks to Wikipedia, I learn it is "an autumn flower in Japan". The commenters say that the "This song is a song of marrying woman and the mother. She parts from mother and lives. It is the song of the day before she leaves the house" [Source]. Interesting how Masha, a man could convey the message. Did he change the lyrics from she to he? From bride to groom? Or just sing it as it is? The original singer is 山口百恵 aka the mega star of her day, Yamaguchi Momoe whose rise was meteoric as was her very early retirement, by choice. I think a lot of girls were named Momoe because of her, much like Chan Po Chu! Since she debuted in 1972 and retired in 1980, I would say this song is pretty old indeed. The above video is from Daikanshasai 2001. You will find this song in his album, The Golden Oldies. I am posting the album version as well as the original version and Romaji and English lyrics after Read More.

Update
I made a terrible mistake! The original singer and songwriter was a male singer, Sada Masashi! Did he write the song for Momoe? His version, a bit high pitched than Masha but very well sung is after the Read More link.




THE ALBUM VERSION
Or rather from his defunct show, Fukuyama Engineering



The album version from the album The Golden Oldies.




THE ORIGINAL VERSION
By Momoe Yamaguchi. Youtube


By the original songwriter, Sada Masashi



LYRICS
ROMAJI VERSION [Source]

Usubeni no kosumosu ga aki no hi no
Nanigenai hidamari ni yurete iru
Konogoro namida moroku natta haha ga
Niwasaki de hitotsu seki wo suru

Engawa de arubamu wo hiraite wa
Watashi no osanai hi no omoide wo
Nandomo onaji hanashi kurikaesu
Hitorigoto mitai ni chiisana koe de

Konna koharu biyori no odayaka na hi wa
Anata no yasashisa ga shimite kuru
Ashita totsugu watashi ni kurou wa shitemo
Waraibanashi ni toki ga kaeru yo
Shinpai iranai to waratta

Are kore to omoide wo tadottara
Itsu no hi mo hitori dewa nakatta to
Imasara nagara wagamama na watashi ni
Kuchibiru kande imasu

Ashita e no nizukuri ni te wo karite
Shibaraku wa tanoshige ni ita keredo
Totsuzen namida koboshi genki de to
Nandomo nandomo kurikaesu haha

Arigatou no kotoba wo kamishimenagara
Ikite mimasu watashi nari ni
Konna koharu biyori no odayaka na hi wa
Mou sukoshi anata no kodomo de
Isasete kudasai

ENGLISH VERSION 1 [Source]
A pale pink cosmos sways
In an ordinary spot in the sun on an autumn day
My mother, who has cried easily recently
Coughs once by the garden

She opens an album by the trees
And talks about memories of my childhood
Over and over again
In a small voice, as if talking to herself

On this peaceful day in an unusually warm autumn
I feel your kindness deeply
I laughed and said
“Even if my getting married tomorrow is causing you pain now
Time will turn it into a funny story, so you don’t need to worry”

“Now I’m looking back on various memories
I’ve realised there was never a day when I was alone”
She bites her lip as she looks at me
Who is still as selfish as ever

She helped me pack for tomorrow
And we kept our spirits up for awhile
But then suddenly Mum burst into tears
And said “Good luck” again and again

I’ll try to live my life my way
With the words “Thank you” in my heart
Let me be your child
A little longer
On this peaceful day in an unusually warm autumn

ENGLISH VERSION 2
Translated by Vspirit


Pink cosmos quietly sway
In the easygoing sunshine of an autumn day
My mother who lately cries easily often
Lets out a single cough as we sit in the garden


Sitting on the veranda she opens up a photo album
And shares with me again and again
The same old stories of when I was little
In a faint voice, as if muttering to herself


On this mild autumn evening so gentle
Your tenderness touches me deep inside
Smiling as you tell your daughter who
Becomes a bride tomorrow not to worry
That all hard times become funny stories in time


Try looking back on all the days past within your memory
And you'll find that there never really was a day when you were alone, honey
Biting your lip, this is what you tell the girl
Who is still as full of herself as ever


Lending a hand as I pack for my big day tomorrow
We spend a long moment enjoying nothing but each other's company
But without warning, you break into tears
Telling me again and again to take good care of myself


Bearing the words 'thank you' within my heart
I shall live the best way I know how
But on this mild autumn evening so gentle
Mother please let me remain your daughter
If only for just a little while longer