Z39b20co13mi01cal09

z39b20co13mi01cal09 (called on the JASRAC database) is Disc 2, Track 6 on the XenobladeX Original Soundtrack. It is split into two parts: the first plays from the start until 1:36, and the second plays from then until the end.

The first part of the track plays in the following cutscenes:
 * In when the party discovers and frees Tatsu from a storage container.
 * In Chapter 3 when Tatsu is introduced to.
 * In when Lin suggests Tatsu make the refrigerator his room.
 * In Chapters 4 through 12, when Lin is cooking and uses Tatsu to make food jokes.
 * In when L approaches the party.
 * In when the party first meet the Ma-non.
 * In the Affinity Mission "A Friend In Need" when Tatsu sympathises with Lao's team members.
 * In the Affinity Mission "The Matchmaker" when the party learns Shingo has a crush on someone.
 * When the party negotiates with the Ma-non craftsman in the same mission.
 * When Lin and Vandham introduce the Skell with the Flight Module to Cross in the Affinity Mission "A Girl's Wings".

The second part plays in the following cutscenes: A very small portion of the second part (1:59 to 2:07 in the track) and no accompaniment plays on the results screen for Squad Missions, Time Attack Missions and Support Missions.
 * In when Lin brings Cross on a tour throughout New Los Angeles.
 * In the opening cutscene of the Affinity Mission "Renewed Will".
 * In the Affinity Mission "Close Comrades" when meeting up with Lao.
 * In the opening cutscene of the Affinity Mission "Then and Now".

Etymology
The track title can be split into 3 parts: the prefix 'z39b', the digits '20130109', and the letters 'comical'. The digits can be interpreted as the date 2013/01/09, or the 9th of January 2013, possibly the date in which the track was composed or recorded. The track is one of several in the XenobladeX Original Soundtrack beginning with 'z' and a number (possibly followed by 'b'); the significance of this is unknown.