Notes:

Serebii says:

The first details of the upcoming special, Mega Evolution Act I have been revealed. This special, due to air on April 3rd in Japan, focuses on a new character called Alan, as well as the Elite Four member Siebold, with other new characters Manon, Louis and Ayaka as they travel and unlock the secrets of Mega Evolution. Alan's goal is to defeat every single Mega Evolution to prove himself as the strongest trainer. This goal leads him to Siebold who has got a Mega Evolution of his own.

Also it's apparently set in the same universe as Ash.