She was also a member, along with her good friends Anna Iriyama and Rina Kawaei, of a one-shot AKB48 subunit named AnRiRe.

She officially participated on AKB48 singles on Chance no Junban's coupling song, titled "Fruits Snow", as part of Team Kenkyusei.

On December 17, 2011, Rena Katō, together with two other members of AKB48, Ami Maeda and Anna Iriyama, held a large autograph-signing event in Hong Kong.

Soon after the TV series Shiritsu Bakaleya Kōkō ended on June 30, 2012, it was announced that Rena Katō would participate in its film adaptation.

In 2014, she got a knee injury and had to temporarily postpone her AKB48 activities, as a result, she was not able to participate in the Unit Matsuri 2014, as well as the AKB48 Request Hour Set List Best 200, except on the final day.

Even with an injury, she and Yuki Kashiwagi held a large autograph-signing and handshake event in Hong Kong with thousands of fans.

It started when Kato made a list of her favorite members on social media at her fans' request, but received the approval of Yasushi Akimoto shortly after and eventually became an official event.