Madrid advanced 3-1 on aggregate, extending their strong home form with a seventh straight win at the Bernabeu and maintaining their record of reaching the knockout stages in every season since 1996/97.
The tie had been overshadowed by an alleged racist incident in the first leg involving Vinicius Junior and Benfica's Gianluca Prestianni. Prestianni was provisionally suspended by UEFA for the return match pending investigation, with Benfica's appeal rejected before kick-off.
"We didn't play our best match of the season, that's for sure," said Tchouameni. "But there are things more important than this match, and more important than football."
After Vinicius sealed the win with Madrid's second goal on the night, Tchouaméni added: "It's a victory for everyone who is against racism."
Vinícius later posted on social media: "The dance continues," alongside an image of a large "No to racism" banner displayed inside the stadium.
Madrid also confirmed they expelled one of their own supporters before the game for performing a Nazi salute. "This member was identified by the club's security staff moments after appearing on the broadcast and was immediately expelled," the club said. "Real Madrid condemns this type of gesture that incites violence and hatred in sport and society."
On the pitch, Rafa Silva had given Benfica an early lead after 14 minutes, reacting quickest when Thibaut Courtois could only parry Raul Asencio's attempted clearance from Vangelis Pavlidis' cut-back. Tchouameni responded with a superb first-time finish from Federico Valverde's cross to level the night.
The decisive moment came when Vinicius collected Valverde's through ball and calmly finished past Anatoliy Trubin.
Head coach Alvaro Arbeloa praised the Brazilian. "I reacted with joy, obviously, for the great goal he scored, and because it was him - he deserves it," he said. "Without Kylian Mbappe it was even more important."
Arbeloa confirmed Kylian Mbappe is sidelined with a knee injury. "We felt the best thing was for him to stop and recover one hundred percent," he explained. "I hope it's nothing major and that he can come back in a few days or weeks."
Madrid now look ahead to the last 16 with momentum - and a clear message off the pitch as well as on it.
FC Barcelona defender Gerard Martin has insisted his side still believe they can produce a dramatic comeback against Atletico Madrid on Tuesday in the Copa del Rey semi-final.
Liverpool FC will discover their route to the Champions League final on Friday, when the draw for the last 16 maps out not only their next opponents but also their potential path all the way to May's showpiece final.
Newcastle United defeated Qarabag FK 3-2 in their UEFA Champions League playoff match at St. James Park on Tuesday to book a spot in the Round of 16.
Barcelona face a defensive selection headache ahead of their crucial La Liga clash with Villarreal this Saturday at the Camp Nou after left‑back Gerard Martin was suspended.
