Konosuba - God's Blessing on This Wonderful World! Vol 18

From the Yen Press edition

Kazuma’s off to Elroad, the land of casinos, but he’s got something more important than gambling on his mind—his beloved little sister, Iris! She’s due to visit her betrothed, a prince from a neighboring country, and has personally requested Kazuma serve as her bodyguard along the way. As he and his party arrive in the royal capital, Lain is hardly moved by his presence. Yet for some reason, Claire seems uncharacteristically eager to talk to him…

Source: Yen Press