Note : Season 1 Episode 9: Encounterdeath

Light is forced to maintain a calm exterior while internally spiraling into a panic. He realizes L has trapped him in a perfect "checkmate" scenario:

If L dies shortly after revealing himself to Light, the Task Force will immediately know that Light is the culprit. EncounterDeath Note : Season 1 Episode 9

To further pressure Light, L invites him to join the investigation, hoping that closer contact will eventually force a slip-up. Key Themes & Analysis Encounter | Death Note Wiki | Fandom Light is forced to maintain a calm exterior

If Light tries to kill "Hideki Ryuga" using the Death Note, he would likely picture the famous idol instead of the person in front of him, resulting in the idol's death and confirming Light is Kira. EncounterDeath Note : Season 1 Episode 9