Don’t ask me why…

上を向いて歩こう
涙がこぼれないように
思い出す　春の日
一人ぼっちの夜

上を向いて歩こう
にじんだ星をかぞえて
思い出す　夏の日
一人ぼっちの夜

　　幸せは　雲の上に
　　幸せは　空の上に

上を向いて歩こう
涙がこぼれないように
泣きながら　歩く
一人ぼっちの夜

思い出す　秋の日
一人ぼっちの夜

　　悲しみは　星のかげに
　　悲しみは　月のかげに

上を向いて歩こう
涙がこぼれないように
泣きながら　歩く
一人ぼっちの夜
一人ぼっちの夜

…but if you must know. [update: changed the link to a site with better romanization and translation]

For amusement, I fed this into Babelfish. My furigana tooltips confused it a bit about whitespace, so I removed them first. It’s better than I expected it to be, based on past experience. I’ve marked the significant errors in red the first time they appear, with literal translations in tooltips.

Facing, you probably will walk on
Way the tear does not spill,
Day of spring when you remember
Night of loneliness

Facing, you probably will walk on
Obtaining whether the star which spreads
Day of summer when you remember
Night of loneliness

As for happiness on cloud
As for happiness on sky

Facing, you probably will walk on
Way the tear does not spill,
Crying you walk
Night of loneliness

Day of fall when you remember
Night of loneliness

As for sorrow to star or
As for sorrow month in

Facing, you probably will walk on
Way the tear does not spill,
Crying you walk
Night of loneliness
Night of loneliness