SacredShipping (Japanese: マツミナ MatsuMina or ミナマツ MinaMatsu) it the belief that Morty and Eusine belong in a romantic relationship. Eusine was introduced in Crystal and is a frequent visitor to Ecruteak City
and its Gym Leader.
They are known to be acquaintances and believed to be friends. The name is derived, in part, from the idea that the material both handle are sacred in some way: Eusine's idolatry of Suicune and Morty's involvement with Ecruteak's mythological and historic environment. Their anime interaction occurs during the episode For Ho-Oh the Bells Toll!.
When conceptualizing the pair together, fans (and some non-fans) of the Ship tend to split themselves into two groups when referencing EP227: those that believe Morty and Eusine are in the midst of a relationship and those that believe a relationship has already taken place and they have split by this point.
Those for the latter cite that Eusine spends the episode ignoring Morty in favor of all things Suicune related, which includes
Ash
's claim to have seen it, and claim Morty doesn't act so much like a jilted lover than someone concerned for Eusine's well-being (as his obsession is nearly unhealthy).
Those for the former believe Morty is acting like a jilted lover in the face of Eusine's quest, and remains beside him out of loyalty and devotion.