Spoiler Alert: The following article has information not currently present in the anime or manga. Do not proceed unless you want to be spoiled.
Yumina Ernea Belfast (ユミナ・エルネア・ベルファスト,Yumina Erunea Berufasuto?) is one of the heroines In Another World With My Smartphone. She is one of Touya Mochizuki's wives. Yumina is also the crown princess of the Kingdom of Belfast and she is currently traveling with Touya and everyone else.
Yumina is a polite and careful person who is an exemplary member of royalty. However, Yumina's actions for a princess are surprisingly bold.
Yumina has long blonde hair with green eyes (most of the time). Before meeting Touya, Yumina wears a dress for a royal attire. Later when joining the guild, Yumina begins to wear a white blouse with a blue ribbon, and a black top over that.
Mystic Eyes - Eyes that allow sight of the true nature or personality of any person a user sees.
Magic - She's able to use 3 attributes which are wind, earth, and dark.
Summoning - Her aptitude toward dark type magic has grants her ability to use summoning magic. She is contracted to 3 kinds of beasts which she can summon, but in the Light Novel the only beast shown is the Silver Wolf meaning that the other beasts are unknown as of volume 4.
Future Prediction (未来予知,Mirai Yochi?) - it is Yumina's "FAMILY TRAIT" (眷属特性,Kenzoku Tokusei?). As a "FAMILY" (眷属,Kenzoku?) of Touya Mochizuki, she is bestowed by Touya's divine power with an ability to see a few second into the future.
Revolver Handgun - Yumina received a handgun from Touya which is made of Dragon Horn. Because it is made of Dragon Horn, the gun is lightweight but its durability is stronger than ordinary iron. The handgun is modeled after Colt Army M1860 with size adjustment to fit Yumina's hand.
Engagement Ring - Yumina received diamond ring made of platinum metal as engagement ring from Touya Mochizuki. The ring is magically self-fit and also enchanted with 【Accel】, 【Storage】, and 【Transfer】 by Touya which allows her to utilize them.
Sacred Ring - Yumina received platinum gold ring from World God as wedding gift which was given through the great spirits. The ring is a sacred treasure which can act as receiver for Touya's divine power.
"I'm happy.. to be a bride of my favorite person was my dream, now... I'm really fortunate" - Yumina before her wedding kiss.