Cactus Flower（サボテンの花 Saboten no Hana） ～from Hitotsu Yane no Shita (ひとつ屋根の下, lit.: "Under One Roof") ～ by Kazuo Zaitsu(財津和夫)

There might be a music video on Youtube.

The lyric is here.

The audio file or streaming to learn Japanese.