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Magnetic helicity (MH) is a measure of twist and shear of magnetic field. MHis injected in the active region (AR) corona through photospheric footpointmotions causing twisted and sheared magnetic fields. From the conservationproperty of the helicity, it was conjectured that an already twisted flux rope(FR) with continuous injection of MH inevitably erupts to remove the excessaccumulated coronal helicity. Therefore, understanding the nature and evolutionof the photospheric helicity flux transfer is crucial to reveal the intensityof the flare/CME activity. Using the time-sequence vector-magnetograms of\textit{Helioseismic Magnetic Imager}, we study the evolution of MH injectionin emerging AR 12257. The photospheric flux motions in this AR inject positivehelicity in the first 2.5 days followed by negative helicity later. Thissuccessive injection of opposite helicity is consistent with the sign of meanforce-free twist parameter ($\alpha_{av}$), orientation of magnetic-tongues.Also, the extrapolated AR magnetic structure exhibits transformation ofglobal-shear without a twisted FR in the core of the AR. No CMEs are launchedfrom this AR but C-class flaring activity is observed predominantly in thesecond half of the evolution period. The ARs with sign reversal of the MHinjection are not favorable to twisted FR formation with excess coronalhelicity and therefore are important to identify CME-less ARs readily. Apossible scenario in these ARs is that when one sign of helicity flux isreplaced by opposite sign, the magnetic field of different connectivity withopposite shear undergoes reconnection at different scales giving rise to bothintermittent flares and enhanced coronal heating.

Successive Injection of Opposite Magnetic Helicity: Evidence for Active Regions without Coronal Mass Ejections