A collection of stories:
1-3. 2 Shuukan no Adventure
5. His Left Eye
A story detailing an encounter between Gerry and Eugene from Barairo no Hoo no Koro, as adults.
6. Belgian Waffle
Andrew, from Barairo no Hoo no Koro, takes a stroll with his old father, bringing about some surprising discoveries, aside from the fact that Belgian Waffles can be sweet.
Timeline (from Oriolidae & Sparviero):
01 Barairo no Hoo no Koro v01 ch01-05
02 J no Subete v01 ch01-05
03 2 Shuukan no Adventure v01 ch05-06
04 J no Subete v02-03
05 Barairo no Hoo no Koro v01 Extra