Senpai! You're Such a Reliable Senpai!

Senpai! You're Such a Reliable Senpai! (先輩! 頼りになる先輩じゃないっすか!) is the third chapter of the Attack on Titan: High School manga, written and illustrated by Saki Nakagawa.

Overview
The students of Attack High infiltrate Marley Academy, going through each of the Nine Traps, before encountering four students that they've never met before.

Summary
At Attack High, Eren and company tell Floch of their plan to infiltrate Marley Academy. Floch warns them that no outsiders had entered Marley without incident. Before Eren can tell him off, the seniors Petra, Oluo, Eld and Gunther enter, claiming that they are joining the mission, with a new "power".

Back at Marley, Reiner and company are tied up and trapped in a closet by Magath, who is upset that Ymir invited more "demons" to enter Marley. When Reiner asks what will happen to the Attack students, Principal Willy Tybur, over video call, tells them that their friends will not be able to enter, due to the "Nine Traps".

Once the Attack students enter Marley, Connie and Sasha immediately fall into a trap and sink into quicksand. The seniors attempt to rescue them with their "new power": Thunder Spears, but argue amongst themselves until Connie and Sasha escape by themselves.

As the Attack students enter Marley's pool, they are chased by what they think is a shark, but is actually a Titan disguised as a shark. The seniors attempt to use the Thunder Spears against the Titan, but they don't work in the water, and the students just barely escape.

The Attack students keep getting caught in the traps, and each time the seniors' Thunder Spears fail to work properly.

Once the Attack students make it to Magath, the seniors cry and ask if they were even needed on this mission. While trying to console them, Eren tells them to use the Thunder Spears at that moment. They excitedly prepare the Spears, and the Marleyan students with Magath ask if the enemies are underestimating them. Once they're prepared, the seniors fire the Thunder Spears at the four students, leaving them covered in whipped cream. Petra apologizes, saying she doesn't know who the students are.

Trivia

 * This chapter was soriginally untitled in its original publication on Bessatsu Shōnen Magazine. The title was added in the tankōbon release.