Tate no Yuusha no Nariagari - Vol. 26 Ch. 108.6

[MangaDex]

 

[Grailm]

...poor Atla

 

[GipoScribantino]

Woah, now that is an old reference.

 

[Hikineet]

Thanks for the chapters.

 

[Liquidxlax]

why does he call him "Alps"?

 

[AsakaraYoruto]

why does he call him "Alps"?

Ah, sorry, just realized the placing of the TLN at the bottom made it hard to see in mangadex browser.
Basically, it's reference to "Heidi, the Girl of the Alps"