Kalos walkthrough section
Pokemon X and Y Phase 5: Lysandre Cafe Revisit
Voltage Badge Plot beat: After restoring the Power Plant, head to Magenta Plaza and visit Lysandre Cafe (across from the central Pokemon Center).
Phase 5 Voltage Badge Clemont Lumiose Gym Leader Route 13, Kalos Power Plant, Lumiose City, and Clemont. 05 / 10 
Phase 5 section 5 of 7
Plot beat: After restoring the Power Plant, head to Magenta Plaza and visit Lysandre Cafe (across from the central Pokemon Center).
GuidePokemon X and Y
PhasePhase 5
Section5/7
Lysandre Cafe Revisit
Plot beat: After restoring the Power Plant, head to Magenta Plaza and visit Lysandre Café (across from the central Pokémon Center). Lysandre is inside. He talks to you about his vision for a "beautiful world" — heavy foreshadowing. Diantha (the Champion) is also briefly present. No battle.
Plot teaser: Lysandre Café has a hidden door behind a china cabinet that leads to Lysandre Labs — Team Flare's actual headquarters in Lumiose. It is NOT accessible in Phase 5. The door requires a password you don't have yet. You'll come back here in Phase 7 after Anistar.
Café Soleil revisit (also recommended)
Sushi High Roller (back booth): Sometimes here. Gives a Star Sweet on later visits if your Pokémon's affection is high enough.
Various Furisode Girls: Now have ~Lv 35 rosters. Easy XP if you want to top up before the gym.