C#
using System.Data.Common;
using Microsoft.EntityFrameworkCore;
using System;
using System.ComponentModel.DataAnnotations;

namespace RexLapis.Database{
    //UserInfoClass represents the Discord user.
    public partial class UserInfoClass{
        [Key]
        public string DiscordId { get; set; } = "";
        public List<string> GenshinId { get; set; } = new List<string>();

        public void Append(string input){
            GenshinId.Append(input);
        }
    } 

    //GenshinIdClass represents a specific Genshin player account.
    public partial class GenshinIdClass{
        [Key]
        public string GenshinId { get; set; } = "";
        public string DiscordId { get; set; } = "";
        public List<string> Characters { get; set; } = new List<string>();

        public void Append(string input){
            Characters.Append(input);
        }
    }
    //
    // Summary:
    //  DBClass represents the database I have, however the database itself will not
    //  be on GitHub.
    public class DBClass : DbContext{   

        public virtual DbSet<UserInfoClass> UserInfo { get; set; }
        public virtual DbSet<GenshinIdClass> GenshinInfo { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder options)
        {
            options.UseSqlite("Data Source=UserInfo.db");
        }

    }
}

C#
using System.Data.Common;
using Microsoft.EntityFrameworkCore;
using System;
using System.ComponentModel.DataAnnotations;

namespace RexLapis.Database{
    //UserInfoClass represents the Discord user.
    public partial class UserInfoClass{
        [Key]
        public string DiscordId { get; set; } = "";
        public List<string> GenshinId { get; set; } = new List<string>();

        public void Append(string input){
            GenshinId.Append(input);
        }
    } 

    //GenshinIdClass represents a specific Genshin player account.
    public partial class GenshinIdClass{
        [Key]
        public string GenshinId { get; set; } = "";
        public string DiscordId { get; set; } = "";
        public List<string> Characters { get; set; } = new List<string>();

        public void Append(string input){
            Characters.Append(input);
        }
    }
    //
    // Summary:
    //  DBClass represents the database I have, however the database itself will not
    //  be on GitHub.
    public class DBClass : DbContext{   

        public virtual DbSet<UserInfoClass> UserInfo { get; set; }
        public virtual DbSet<GenshinIdClass> GenshinInfo { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder options)
        {
            options.UseSqlite("Data Source=UserInfo.db");
        }

    }
}