We present the first results from the ongoing Lyman Alpha Galaxies in the Epoch of Reionization (LAGER) project, which is the largest narrowband survey for z similar to 7 galaxies to date. Using a specially built narrowband filter NB964 for the superb large-area Dark Energy Camera (DECam) on the NOAO/CTIO 4 m Blanco telescope, LAGER has collected 34 hr NB964 narrowband imaging data in the 3 deg(2) COSMOS field. We have identified 23 Ly alpha Emitter candidates at z = 6.9 in the central 2-deg(2) region, where DECam and public COSMOS multi-band images exist. The resulting luminosity function (LF) can be described as a Schechter function modified by a significant excess at the bright end (four galaxies with L-Ly alpha similar to 10(43.4 +/- 0.2) erg s(-1)). The number density at L-Ly alpha similar to 10(43.4 +/- 0.2) erg s(-1) is little changed from z = 6.6, while at fainter L-Ly alpha it is substantially reduced. Overall, we see a fourfold reduction in Ly alpha luminosity density from z = 5.7 to z = 6.9. Combined with a more modest evolution of the continuum UV luminosity density, this suggests a factor of similar to 3 suppression of Ly alpha by radiative transfer through the z similar to 7 intergalactic medium (IGM). It indicates an IGM neutral fraction of x(HI) similar to 0.4-0.6 (assuming Ly alpha velocity offsets of 100-200 km s(-1)). The changing shape of the Ly alpha LF between z less than or similar to 6.6 and z = 6.9 supports the hypothesis of ionized bubbles in a patchy reionization at z similar to 7.