Kigen Summon : Behind the Smile Kigen Summon : Behind the Smile is the sixteenth episode of " " . Story Detail . The First Test . Now ensnared in the Ocean Puzzle , Jane is transported to the first challenge of the Puzzle . When Jane lands , the crew recovers and survey their surroundings : They are currently resting on a pillar of stone , high above the water , in a cube of space . From the roof / sky of the cube , a gigantic mermaid like fish descends . She explains that she is here to give the group a series of riddles as their test for this cube . She demands they elect three people to answer her riddles , and to stand for them . After a brief discussion , the crew agrees to comply , and Lisa , Knave and Miles are elected to answer the riddles . Fear the Fish . Presenting themselves to the mermaid , the three prepare for the riddles . Knave is chosen to go first , and in given a seemingly simple riddle : " In the beginning it has four legs , then it has two legs , and finally three . What is it ? " Knave announces that it must be a human , but the mermaid says this is incorrect , claiming the correct answer was a bacteria creature called " Hemora " . For answering incorrectly , the entire cube of space moves toward the bottom of the puzzle . Similar questions and results follow , with Knave answering all three questions incorrectly . When the answer of the third question is announced , Knave melts into a puddle of liquid . Miles volunteers to go second , but she meets the same fate . Truth . The mermaid announces that they do not have any further to fall , and thus the next question will decide their fate ; death or salvation . She presents a complex question to Lisa , one she couldn ' t possibly answer . The others falls into despair , waiting for her answer with baited breath . As she tries to think , her thoughts wander into her memories , as she recalls her mother dying defending her village , and what she told Lisa on her deathbed . The mermaid urges her to answer , breaking into her thoughts . As she tries to recollect herself , Kaze appears behind her , and simply tells her there is no answer . With sudden understanding she announces to the mermaid there never was an answer to begin with ; she was simply saying something other than what they answered each time . Despite Lisa ' s victory , the mermaid refuses to allow them to live , and begins destroying the cube in which they exist . A cascade of water falls from the sky , blasting the submarine and pinning it to the rock surface . Lisa , in an act of desperation , sacrifices herself to allow the others to live , by using her Kigen arts to summon a serpentine creature using her own life force . The creature lifts Jane through the torrents of water effortlessly . Having carried them to safety , Lisa dispels the creature , allowing herself to fade , with the last thing she sees being Kaze reaching out for her wordlessly . Epilogue . Somehow , despite using her life force to summon the creature , Lisa awakens aboard Jane . Knave and Miles have also been revived somehow . Cid theorizes that the energy contained in the water rendered her life force unnecessary , thus allowing her to survive . Seeing Kaze is still with them , Lisa smiles a true smile , and Jane moves on to the next cube .