Chu-Bra Step 27 is up on the Biribiri site
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But not on the "read online" site.
You can either DL the chapter, or all of Tankoubon 4.
In this chapter, the girls are measuring each other (or trying to) in the girls' dressing room, when Amane, the cross dressing boy, gets roped into joining them and has to admit he's a boy. The story stops half-way through, as a cliff-hanger to the next chapter.