Tsunderplane is an enemy that appears in Hotland.
Tsunderplane appears to be a regular real-world airplane wearing a pink mob cap with thin ribbons on it. Tsunderplane also has a faint blush.
It is fixated on the protagonist in a manner unswervingly modeled off of the "tsundere" character archetype for which it is named. It has romantic feelings for the protagonist, but refuses to admit it, and wavers between acting flustered, defensive, or snubbing in turns, unless the protagonist gets Tsunderplane's guard down.
- Several planes fly horizontally straight from either side of the Bullet Board, dropping bombs. Once a bomb hits the bottom of the board, a vertical line of smoke appears that goes through the whole board.
- Large planes fly from the top to the bottom of the board, leaving a horizontal-moving smoke trail.
- In a turn after approaching, the planes are surrounded by narrow green zones and the smoke trail does not move across the board.
- If the protagonist uses the "Approach" ACT, its attack's airplanes are now surrounded by narrow green zones.
- Touching the green zone (4 times if by itself, or 3 times with Vulkin) allows Tsunderplane to be spared. However, unlike other Green Attacks, this does not heal the protagonist.
- Touching the white part of the plane still causes damage.
- No way! Why would I like YOU [Check]
- It's not like I LIKE you. [Neutral]
- Id... Idiot! [Neutral]
- Hmph! Don't get in my way! [Neutral]
- Human, I... [Neutral when spareable]
- >_<... Human... [Neutral before ACTing]
- Huh!? Y-you sicko! [Flirt before approaching]
- Ah... is that true...? [Flirt after approaching]
- Eeeeh? H-human...? [Approach]
- B-but I never got to...! [Upon being killed]
- Seems mean, but does it secretly like you? [Check]
- Tsunderplane gets in the way! Not on purpose or anything. [Encounter]
- Tsunderplane attacks! Not because it's jealous Vulkin is paying attention to you! [Encounter with Vulkin]
- Tsunderplane gives you a condescending barrel roll. [Neutral]
- Tsunderplane looks over, then turns up its nose. [Neutral]
- Tsunderplane shakes its nose dismissively at you. [Neutral]
- Smells like an airport perfume counter. [Neutral]
- Tsunderplane "accidentally" bumps you with its wing. [Neutral]
- You tell Tsunderplane it has a powerful rudder. [Flirt]
- You tell Tsunderplane you like its taste in movies and books. [Flirt]
- You tell Tsunderplane it has an impressive wingspan. [Flirt]
- You tell Tsunderplane it has cute winglets. [Flirt]
- You tell Tsunderplane it has nice turbines. [Flirt]
- You get close to Tsunderplane. But not too close. [Approach]
- Tsunderplane looks away shyly. [Spare conditions met]
- Tsunderplane's body is smoking. [Low HP]
- Killing Tsunderplane makes it crash and explode like a real airplane, instead of turning into dust as most monsters would.
- This death suggests that Tsunderplane is a mechanical monster, similar to Mettaton. It is possible that Tsunderplane is a ghost like Mettaton. However, it is also possible that Tsunderplane is an airplane-like monster, whose dust is hidden by the explosion.
- The sound that plays when Tsunderplane becomes spareable is also used when the protagonist gets a question correct in Mettaton's quizzes.
- Tsunderplane, along with Jerry, is one of the few monsters whose Spare method differs depending on who is also present in that battle.
- When spared, Tsunderplane's sprite becomes smaller and hatless, and moves to the top left corner of the screen. This may be a side-effect of Tsunderplane's unique death animation, which includes Tsunderplane's hat falling off.
- If Vulkin is present after doing this, it explains that Tsunderplane becoming small is intentional.
- Tsunderplane resembles an Airbus A340-300.
- Tsunderplane is mentioned in Mettaton's news ticker, which reads "LOCAL PLANE CREATES HUGE LINE AT STORE BY SAYING "IT'S NOT LIKE I WANT TO BUY THESE PRODUCTS OR ANYTHING" CASHIER CONFUSED."
- Tsunderplane does not appear to tell the story of Asriel Dreemurr in New Home.
- Tsunderplane might be a pun for "Thunder Plane." It also appears together with Vulkin that uses "thunder" attacks.
- Tsunderplane can be seen in Hotland after the completion of the True Pacifist Route. It explains to the protagonist how it did not love them but instead was enamored with the concept of love. However, at the end of the conversation, it still says "Y... y-you i-idiot," leaving ambiguity on whether what it just said was true or not.
- One of Tsunderplane's attacks encourages grazing (getting close to a bullet without touching it), a mechanic that originated from the Touhou Series.