In this game the character "Ein" or MC childhood friend is merely support character with almost none attack except for a sigle enemy earth and thunder spell.
I believe this character would be best used if he gained an area thunder spell, it would help in the first Exam (village investigation) with all those poison slimes in the sewer catacombs under the village.
Because in this game demo it's better to strenghten relationship with the other 3 characters:
1) Alyssa (Area Nature Spell)
2) Jin (Area Fire Spell)
3) Lunelle (Area Water Spell)