(This was actually super easy to find as Brassius has only been in a couple episodes and I actually meant to answer this yesterday but I fell asleep and lost motivation...)
For context:
The Rising Volt Tacklers (which Liko is a part of) are in Paldea because there were sightings of the black Rayquaza that came out of Roy's (one of the other protagonists) Ancient Poke Ball. In episode 9, Liko returns home and at the end, hears from her dad, Alex, that an artist in Artazon, Brassius, has seen a rare Pokemon that could be the Rayquaza.
In episode 10, which is where this scene comes from, Nemona takes Liko and Roy to Brassius, where they find him smashing one of his sculptures. Brassius looks so on edge, making Liko anxious, and she nervously introduces herself, saying:
"Um my dad Alex is a picture book artist I heard you were acquainted so if you don't mind I was hoping you could maybe answer a question for me. Oh yeah and my name is Liko." (Dub)
"U-um, I heard you knew my father Alex, who makes picture books, so I thought I'd pay you a visit! My name's Liko!" (Sub)
In response, we get to the scene in the GIF where Brassius is saying:
"Alex the picture book artist you say
Ah, you mean THE Alex, oh myy!" (Dub)
"Someone who makes picture books...
Oh, you mean that Mr. Alex?!" (Sub)
The bottom line of the quote is when he's getting close.
So yeah, basically, he's being a fanboy for Liko's dad. Which I guess is fitting, in a way. And yes, I meant to say something other than 'a fanboy' but I decided against it.
Hope you found this interesting!