TOKYO, May 13 (Reuters) - Japanese shares ended lower on Monday as investors grew cautious ahead of corporate earnings reports, while rising Japanese government bond yields weighed on sentiment.

The Nikkei inched down 0.13% to close at 38,179.46, after slipping below the 38,000 level for the first time since May 2 earlier in the session.

The broader Topix was down 0.15% to 2,724.08.

"More local companies are set to announce their outlook but many of them are expected to be conservative so investors were cautious about buying stocks," said Shoichi Arisawa, general manager of the investment research department at IwaiCosmo Securities.

Mitsui Fudosan tanked 5.39% as the developer's annual net forecast was below market expectations. Peer Mitsubishi Estate fell 4.11%.

The real estate sector lost 3.26% to become the worst performer among the Tokyo Stock Exchange's 33 industry sub-indexes.

Chip-making equipment maker Tokyo Electron fell 1.03% to become the biggest drag on the Nikkei.

Earlier in the session, the Bank of Japan cut the amount of Japanese government bonds it offered to buy in a regular purchase operation, sending Japanese government bond yields higher.

"The move was taken as negative for the stock market as this is a step closer to the normalization of the BOJ's policy, which raised expectations for a further rate hike," Takehiko Masuzawa, trading head at Phillip Securities in Tokyo.

Among the gainers, Olympus surged 9.65% after the medical equipment maker reported its annual operating profit would quadruple and announced a share buyback.

Honda Motor rose 1.12% after the automaker said it would buy back up to 3.7% of its own shares worth 300 billion yen ($1.93 billion).

KDDI rose 3.69% after the mobile phone company announced a similar move.

Of the 225 Nikkei components, 87 stocks rose and 136 fell, while two were flat.

($1 = 155.7600 yen) (Reporting by Junko Fujita; Editing by Rashmi Aich and Sohini Goswami)