UPDATE 2: [Feb 9th] I updated the song to iron out some rough edges. I hope you like this version better! I will be uploading the localized lyrics later on and hopefully compare them too. The officially translated lyrics for the English version (“Lost in Thoughts All Alone”) can be found here. .Though, they are vastly different as it is a “localization” rather than a translation.
UPDATE: The officially localized title for this song is “Lost in Thoughts All Alone.” The preview lyrics (shown in the final Smash Bros announcement video on Dec. 15 2015) already shows significant differences between the songs, but I will wait for an official lyrics release or transcription before comparing them!
A user on serenesforest.net kindly pointed out that the official Japanese lyrics to the full song of “if~one’s thoughts~” had been uploaded. So I translated them best I could. The song is called if~hitori omou~ in Japanese.
The format is: English. Kanji, and then Romaji.