Pokémon: My Online Friend Is Cynthia

Julian Veyne transmigrated into the Pokémon world and became the eldest son of the Veilstone Gym family. His father was unreliable. His little sister, Maylene, was a natural monster. And Julian himself? Weak body. Poor talent. The only thing he seemed to inherit from the Veyne family was the pink hair. Just as he was preparing to take over Veilstone Gym, his Pokémon Simulator finally awakened. At the same time, his long-time online friend, who had always hidden behind a pseudonym, suddenly arrived at his door with flowers in hand. It was Sinnoh Champion Cynthia! — Description from novelcodex.org