Induction motor: T-Slip Characteristics look weird
Can someone who knows what's going on explain it to me?


It looks pretty normal to me; as you increase torque the motor slips a little more. Maybe the graphical representations you have previously seen look different but are reflected in your diagram. For instance, here's one that looks pretty similar: -



Picture from here.

And your graph appears to be coinciding with "the stable region". But, if you looked at this graph that shows torque against speed you might get confused: -



Taken from a stack exchange question.

In this graph the right hand side of the characteristic is where you graph begins because it shows speed and not slip on the x-axis.