crystal, 122 bytes

Result

AC

Duration

2384ms

Code [DL]

a="#{gets('_')}"
t=a=~/T/||0
h=a.count('\n')-1
k=(a=~/K/||0)%51
puts (a.lines[0]+'\n')*h
puts " "*k+"K"*(t-k+1)+" "*(49-t)

stdin

                    T                             
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
      K                                           

stdout

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                    T                             
      KKKKKKKKKKKKKKK                             

stderr

strace