Qing dynasty leased their land to the powerful nations which are capable to develop and cultivate it. Manchuria is in North East of China beyond Great Wall, a fatherland of Manchus. Japan had a concession leased by Qing and the right to own railroad in Manchuria taken over from Russia by Treaty of Manchuria (満洲善後条約) in 1905 (See Japan never invaded in a modern era) . After Xinhai revolution in 1911, Japan was in trouble since the owner of concession in Manchuria, Qing dynasty, lost a power. Japan had treaty with a new leader of Han Chinese government, Yuan Shikai, yet he died soon, and multiple Han Chinese dictators claimed Manchuria.
This page shows more specifically what rights Japan had with what treaties and how they were violated by Han Chinese, and the individual cases of the damages on railroads, which referred to as Manchuria and Mongolia disorder state problem (Man mou mon dai 満蒙問題).
The historical documents written at that time in 1932 below explain in details. In this section, since many of contents are redundant, their summaries are shown.
The Construction of New Manchuria and Mongolia: Appendix - Map of Manchuria and Mongolia in the Current Situation 新満蒙の建設 : 附・時局満蒙地図
Iron-Blooded Resolution? : The Truth Behind the China-Japan Pending Issues 鉄血解決? : 対支懸案の真相
Army Ministry Pamphlets (9 volumes) 1931, 陸軍省パンフレット９冊 昭和６年
Multiple Han Chinese leaders claimed Manchuria and harrassing Japanese property with a tax or agitating people into anti-Japanese.
People and railroad were often terrorized by local bandits or those agitated by anti-Japanese fractions.
You may think “then, why not give it up? it is out of Japan.“ But Japanese couldn’t. Because it was a special right Japan finally took after going through costly wars.