Liar

Liar (ライアー, Raiā) is the fortieth chapter of the Nisekoi manga series written and illustrated by Naoshi Komi, published weekly in the magazine Weekly Shōnen Jump.

Summary
In the beginning of the gang's summer vacation, Tsugumi invites the gang to Raku's home for a study session. In Raku's room, Tsugumi finds mysterious machine that she thought could use for recreation for study breaks.

A flashback plays where Claude calls in Tsugumi to introduce her to the machine. He tells Tsugumi that the machine is a special lie detector with a 98% success rate. Claude tells Tsugumi that he wants to expose Raku and find his weaknesses with this machine.

After the flashback, Raku wants to try the machine but is reminded by Chitoge that they are fake dating and that the machine could be a way for Raku to get exposed and that he must be in caution. The gang then passes around the machine asking several questions to each other like if Raku truly loves Chitoge (which was mysteriously showed up as the truth on the machine), the chest sizes of Tsugumi and Kosaki from Shū, and Raku's type of girl.

In the end of their "study session", Tsugumi was unable to expose Raku and retrieves the machine once everyone leaves. Tsugumi tries to test out the machine and says that she likes Raku. The machine doesn't react which means that Tsugumi was telling the truth much to her surprise. At that moment Raku walks in and sees that Tsugumi is still at his home and notices that the machine was actually unplugged. Pissed off at the machine for making her believe that she actually likes Raku, she destroys it.

Trivia

 * This is the first study session the group have with Marika.
 * This is the gang's second time having a study session in Raku's home.