Much like Earth snails, Tsumuri have a strong and sticky foot. They use this to cling to surfaces and slowly crawl along regardless of their angle or orientation, allowing them to travel up walls and along ceilings.
In Return of Samus, Tsumuri are encountered early in Phase 1 as Samus makes her descent into the tunnels below. They are also found in Phase 3, in a vertical shaft connecting the area's large cavern to the Metroid-infested catacombs below. They travel along aimlessly and do not react to Samus's presence.
In Samus Returns, Tsumuri are significantly more common, now found in many areas of SR388. Their hard shell now protects them from some beam weaponry, making the face their only weak point if Samus has not yet acquired the Wave Beam or Plasma Beam, does not use Missiles.
Tsumuri are even less hostile than their original appearance. Instead of merely ignoring Samus, they actively flee from her. As they make their escape, they release a toxic slime trail that is left in their wake and will harm Samus through all Suit upgrades. She must wait for the acid to dissolve before she can safely pass through the area.
A new Tsumuri variant is introduced, known as Stronger Tsumuri. These Tsumuri have red skin, more closely resembling the original Return of Samus artwork. Unlike normal Tsumuri, Stronger Tsumuri are constantly discharging their toxic slime, even when they are not threatened. Instead of fleeing from Samus, they charge forward in the direction that they are currently facing, potentially trying to ram into Samus with their tusk-like appendage.
Metroid II manual
- "This snail-like creature has very sticky legs and will creep along the walls and ceilings of the caverns."
- Inhabitants & Eco System of SR388 (p. 17)
- "Tsumuri are giant snail creatures that use their toxic slime as a defense mechanism. Most Tsumuri you encounter peacefully crawl around their area, only releasing toxic slime when approached. There are, however, the red Stronger Tsumuri that constantly leave behind slime trails, but even these aren't aggressive. They’re often easily avoided or defeated. If you don't have a clear path around them, don't attempt to move forward without defeating them first."
- Walkthrough (p. 45)
- "If you choose to explore the high-temperature area beyond the Charge Door, you're immediately greeted by this little fella. Tsumuri aren't tricky enemies to deal with—three missiles and they're done—but they can be troublesome. They coast slowly up and down walls and platforms, but if threatened, they run away while discharging an acid-like substance in their wake. Standing in that substance for more than a second causes you to take continuous damage as long as you're in it. Tsumuri's hard shells also make defeating them difficult without an explosive weapon, in which case every encounter becomes a slow, somewhat careful endeavor."
- Walkthrough (p. 128)
- STRONGER TSUMURI
- "Stronger Tsumuri are faster than their blue counterparts. More accurately, they always move at a fast pace, whereas regular Tsumuri only move fast when scared.
A bigger difference between this Tsumuri and the one you’re used to is its slime trail. Regular Tsumuri only leave a trail of acidic slime when threatened, but Stronger Tsumuri create a continuous trail of slime.
Stronger Tsumuri are more predictable than regular Tsumuri because they don't get startled; they do, however, charge at anything that approaches them. Shoot them with missiles at a distance to avoid potential problems."
- The Tsumuri's name is derived from the Japanese word for snail (カタツムリ katatsumuri ).
- In Return of Samus, Tsumuri behave identically to Moheeks and Needlers, in addition to many other lifeforms on different planets.
- It is unknown whether or not the Tsumuri species became X Parasite hosts, as Samus did not encounter any Tsumuri in Metroid Fusion.
- According to Metroid: Samus Returns Official Guide, the term "Tsumuri" can be used as either a singular or plural noun.